Aces High Bulletin Board
General Forums => The O' Club => Topic started by: eskimo2 on July 27, 2005, 07:23:18 PM
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I was looking at gas prices today:
87 octane was $2.29 a gallon
89 octane was $2.39 a gallon
93 octane was $2.49 a gallon
With such high prices these days, and relatively little difference in price, is it worth spending about 9% more to get about 9% more octane? Will the higher stuff produce better mileage?
(I have an 89 Volvo and a 97 Ford Van)
Thanks,
eskimo
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Basically, you should just get rid of both.
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Ya, the Higher Octane gas would be better. It gives u most power and gas milage because it will burn hotter and more violently. this means that u have to use less of it. I use mid grade in my truck and it gives me one or two more miles to the gallon. lol so now i get 10 miles to the gallon booya:aok
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You won't have any benefit of higher test gas unless you have high enough compression to use it.
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What rabbit said...higher octane is only useful if you have pinging in your engine(gas burning off too quickly) Higher octane only means it has a higher boiling point.
With that said, there are some engines that require high octane. I doubt your Volvo or van are set up this way.
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Originally posted by superpug1
Ya, the Higher Octane gas would be better. It gives u most power and gas milage because it will burn hotter and more violently. this means that u have to use less of it. I use mid grade in my truck and it gives me one or two more miles to the gallon. lol so now i get 10 miles to the gallon booya:aok
You will not reap ANY benefits from using a higher octance than your engine is rated to use. You're only damaging an engine.
Karaya
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find out if summit racing on I76 east of town still has their weekend tuning clincs
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Karaya? It has no benefits but I don't believe it damages the engine.
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My 1973 Olds 98 runs well on the 93 octane, but has a tendency to ping a little on shutdown. Maybe a carb problem though.
Not sure what gas it was designed for, leaded or not, but it does ok with the 93 octane unleaded. It's a road cruising machine. This is the low compression 455 engine 10.5 to 1.
One of the few pleasures I get outta life is driving that car, so gotta pay the price for gas. My philosophizing is it would give a little more than average protection in a fender bender. Justifies the gas price.
But we all know that a car like that is just plain 'ol cool.:D
Man I saw a 1972 or so Buick Centurion couple days ago and that car looked good. I love old Buicks and Oldsmobiles. Those cars need the 93 octane to run and perform like they were meant to.
Les
:)
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I don't know what u are complaining about.
Los Angeles:
87 $2.45ish to $2.55
89 $2.60ish
91 $2.70ish to $2.80
Gas could still be $3,00 I would still keep my 1973 455 engine as a daily driver runing on 91. I don't care. I pick a car on the fun factor, not on gas mileage.
It's now or never, because when u will be old driving your electric car, you would have wished you would not have wasted gazoline on a Honda Civic.:o
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I wouldnt whine about those prices. :)
Here 1 liter 95 octane (0,26 gallons) costs about 1,40 eur.
So 1 gallon costs about 5.3 eur = 6.2 dollars
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The Volvo might be the only one I'd consider running higher octane in. Unless you are having a problem with ignition knock or clatter run the 87 octane and use a bottle of good injector cleaner in your gas every time you change oil.
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Originally posted by rpm
The Volvo might be the only one I'd consider running higher octane in. Unless you are having a problem with ignition knock or clatter run the 87 octane and use a bottle of good injector cleaner in your gas every time you change oil.
or add a quart of diesel fuel to your tank at every other fill up. ;) it will do the same. Ive never had injector problems since an old mechanic suggested that years ago.
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The only thing gasoline with too much octane will do for your vehicle is make it less efficient. SOME of the high octane has a lot of additives in it that will create excessive deposits when they are not burned.
Older vehicles can be ajusted so that they perform better and are more efficient with more octane, but it takes serious tuning to make the most of it, and the gains aren't worth it unless you just like to fool with it.
Newer vehicles will sometimes adjust to the high octane gas by SLIGHTLY leaning the mixture and increasing the timing. However, they are designed to require less octane with the same compression ratio and timing as older vehicles.
Increased timing lead actually creates NEGATIVE torque, by firing earlier in the stroke, before the piston reaches TDC, actually trying to force it down. It does increase cylinder pressure though, making it more efficient. But even more efficiency can be had by increasing the copmression ratio to gain cylinder pressure, and decreasing timing lead. You get the same cylinder pressure, with no negative torque. That's why you see increased compression ratios these days.
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Originally posted by Leslie
My 1973 Olds 98 runs well on the 93 octane, but has a tendency to ping a little on shutdown. Maybe a carb problem though.
Not sure what gas it was designed for, leaded or not, but it does ok with the 93 octane unleaded. It's a road cruising machine. This is the low compression 455 engine 10.5 to 1.
But we all know that a car like that is just plain 'ol cool.:D
Man I saw a 1972 or so Buick Centurion couple days ago and that car looked good. I love old Buicks and Oldsmobiles. Those cars need the 93 octane to run and perform like they were meant to.
Les
:)
I sincerely doubt your unbuilt 455 runs 10.5:1 stock. Pretty sure stock for those was in the neighborhood of 8:1 which has no use for high test gas. I don't have the book and maybe someone else knows for sure but I'll bet a neener neener on it..!
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Originally posted by eskimo2
With such high prices these days, and relatively little difference in price, is it worth spending about 9% more to get about 9% more octane? Will the higher stuff produce better mileage?
(I have an 89 Volvo and a 97 Ford Van)
Thanks,
eskimo
Only if the manufacturer REQUIRES a min. octane rating (High compression engines)
I must run a min. of 90 octane since I fall into this catagory. Otherwise you're just wasting your money.
If your engine is pinging going up hill, just bump the octane up one notch (like from 87 to 89)
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Originally posted by rabbidrabbit
I sincerely doubt your unbuilt 455 runs 10.5:1 stock. Pretty sure stock for those was in the neighborhood of 8:1 which has no use for high test gas. I don't have the book and maybe someone else knows for sure but I'll bet a neener neener on it..!
Well Rabbit, you win. I sure as heck can't afford to bet that. I read it in a manual somewhere I suppose.:)
Les
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Originally posted by RightF00T
Karaya? It has no benefits but I don't believe it damages the engine.
All of the negative impacts the Virgil Heights explained, will USUALLY go unnoticed. They are not GOOD for the engine at all, hence....
Karaya
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There were no stock 455 Olds engines rated higher than 10.25:1.
Only a blueprinted engine will reach that. They actually run around 9.5:1. Because the Olds has a really sorry combustion chamber, they still require high octane at 9.5:1.
The low compression Olds is rated around 9:1. but is actually about 8.5:1. The 73 98 engine fits this category. And it needs the octane because the chamber sucks.
My old 455 had about 10.4:1, because I decked the block and milled the heads to spec. Makes a HUGE difference. You think you've got torque now? Still ran on 93 octane gas, although with less than stock timing.
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FWIW:
I have a Ford Truck that, when fully loaded with the truck camper on the back, and pulling a boat, will ping when going uphill. I carry one tank of fuel with 89 octane and one with 87. When I climb big hills, I switch over to the 89 octane tank and the pinging is gone. SOmething to think about if you're a truck owner, carrying and/or pulling a heavy load.
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My 1973 pontiac 455 is 8.5:1, but I have to 91. Maybe the 1972 455HO had a higher CR, definitly the 1970 400.
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Originally posted by SFRT - Frenchy
My 1973 pontiac 455 is 8.5:1, but I have to 91. Maybe the 1972 455HO had a higher CR, definitly the 1970 400.
You need a 74 SD 455.
There were a few high compression engines built in 71, even fewer in 72, and they were gone by 73. The catalytic converter:rolleyes: arrived, necessitating the use of unleaded fuel. Lead was at the time the primary octane boosting additive.
Even before then, Pontiac, Buick, and Oldsmobile were using lower compression than Chevrolet. Chevrolet had a thing for 11:1 and 11.5:1 compression. The others rarely exceeded 10.5:1.
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Originally posted by Captain Virgil Hilts
You need a 74 SD 455.
There were a few high compression engines built in 71, even fewer in 72, and they were gone by 73. The catalytic converter:rolleyes: arrived, necessitating the use of unleaded fuel. Lead was at the time the primary octane boosting additive.
Even before then, Pontiac, Buick, and Oldsmobile were using lower compression than Chevrolet. Chevrolet had a thing for 11:1 and 11.5:1 compression. The others rarely exceeded 10.5:1.
Yeah I dont think Pontiac ever ran a 11 to 1 motor in a factory car.
Most were 10.25 and 10.50
I think the ram air IV motors were 10.75 to 1.
the 350 horse 400 from my goat that I had rebuilt was 10.5 to 1, but I had TRW forged pistons put in on the rubuilt and had them dished, so the compression was 9.65 to 1.
Ran great on 92, when it was in tune. On really hot days though it would ping a bit, so I always had some octane boost in the trunk.
They are right, unless the car states a higher octane you are just wasting you money running it.
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If you are a pro-capitolist, patriotic American you will buy premium fuel whether you need it or not.
Speaking of fuel....
Gotta give the old "attaboy" to Exxon/Mobile for a 32% jump in profits this last quarter! They're on target for busting wide open last years world record for corporate profits. Which was over 25billion and set by Exxon/Mobile!
And kudos to the House of Reps for approving a massive energy plan which included billions in tax breaks and subsidies to energy companies (like Exxon/Mobile). Lawd knows they needed it! Must be part of that trickle down economy thing they've been talking about for the past 4-5 years.
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FYI,te SD actually started in 1973 (think screaming eagle), in 74 the body changed, the front was inclined to allow the 5mph bumper.
I checked my book, i was wrong, my 1973 455 is only 8.0 (rdy for a blower hehehe), the SD is 8.4 and the 1970 400 is 10.5:1.
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And kudos to the House of Reps for approving a massive energy plan which included billions in tax breaks and subsidies to energy companies (like Exxon/Mobile). Lawd knows they needed it! Must be part of that trickle down economy thing they've been talking about for the past 4-5 years.
And if things are still on track, an 8 Billion gallon/year ethanol mandate as well to help out ADM :aok There were a few useful items in the bill, but by and large a subsidy fest all the way around.
Charon
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Semi agreed with you Charon on the relative value of the energy bill... It does some good things but it does them with tax benefits, not outright legislation.
One thing I am NOT pleased with is the funding to boost the use of ethanol in motor fuel. Back in 1998 and 1999 before the entire country went to crappy alcohol laced fuel, I'd get up to 34 mpg in my 305hp TransAm. The difference back then was amazing... I could fill up in CA and get barely 26-27 mpg on the freeway, but as soon as I was running nevada or arizona gas, I'd be up well above 30. Nowadays, the best I can get is about 28 and it's all because of the non-gasoline additives that reduce the energy content of the fuel. Alcohol oxygenates the engine which is great for emissions, but it lowers the overall ability of the engine to produce power from the fuel because there is simply less energy in alcohol than in petroleum.
When some "normal" reasonably high-output engines (power per liter) can be classed as "ultra low emission" powerplants even with today's fuel, it makes me believe that the whole ethanol in fuel (and that crap that gets put into CA gas that smells funny) thing is just a clever bit of lobbying by the farming industry. They found that the Calif fuel additive is incredibly long-lasting in the environment and it is contaminating every water source in the state, but there are some powerful lobbying forces behind it so the environmental lobby is torn between goals - They want the water to be pure but this additive reduces emissions by a little bit. So California get funny smelling gas and contaminated water, and someone gets rich selling a government mandated fuel additive.
As for high octane, any car with a computer that is aggressive enough to REALLY tweak the fuel/air mixture and timing will benefit from higher octane gas. Even the 1993 nissan micra I drove around the UK for a while (a bit under 60 hp if I recall correctly) would get a measurable 5-6 hp boost from running high octane fuel instead of regular, simply because the engine control computer was aggressive enough to take advantage of the high octane. Many cars have simpler/cheaper computers however, and they simply won't make aggressive enough corrections for the fuel to make a difference.
In my TransAm, the difference between low and high octane fuel is in the neighborhood of 30hp and 5 mpg. The high octane fuel is much better overall, although I have noticed an increase in low rpm torque with the tax-subsidized low octane fuel I get on base here. That makes it a bit easier to drive on a daily basis but my mileage is around 23 mpg when it should be around 27 mpg. But there's no way in heck I'm gonna pay $7/gal for the good stuff so I'll just keep buying the cheap stuff and hope it doesn't wreck my cats and sensors. It's already clogged my fuel filter after a year and a half but those are pretty cheap/easy to replace.
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My friend dyno'd his Ninja 600 and actually LOST horsepower with higher octane. Went from 86 to 82 if I recall...
g00b
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It is very possible to lose power from excess octane, because the fuel cannot be burned properly.
We have crate engine:rolleyes: classes around here, and it took quite some time to convince people that race gas was unnecessary and cost them power. I proved that on the dyno.
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My '90 Cadillac was supposedly an 8.5:1 compression ratio and yet it needed 91 octane fuel (and I did get pinging if I pushed it when running on 87). It had the 4.5 litre v-8 and was rated for like 190 horsepower. That engine must have really sucked...but then I suppose that's to be expected, most engines built in the '80's sucked. I still miss that car. Even the way the gas pedal was heavy yet hyper-sensative to the smallest movement was just perfect.
The LT1 in the Buick runs fine on 87 with a 10.5:1 ratio. It spins the tires of this massive car with remarkable ease. It also gets better mileage than the Cadillac, despite being much more displacement (350 cid versus 273) and moving an additional thousand pounds of car.
If I could have had that LT1 engine in the '90 Cadillac, it would have been the perfect car.
J_A_B
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There were a few Cadillacs with the LT1. I have a friend who worked at a Cadillac dealership. A couple of guys in the cleanup department got fired for doing funny car style water burnouts in new cars. The Cadillac built on the same platform as your Buick will have an LT1. I think they were Fleetwod Broughams.
The ragged 4.1 engine did suck, the 4.5 was not too much better, the final version, the 4.9, was decent.
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heres what i run i my ride.
Cat 3406E
Cylinders: In-line 6
Aspiration: Air-to-air
Bore x stroke: 5.5 X 6.75 in.(140 x 171 mm)
Displacement: 966 cu. in. (15.8L)
Dry Weight: 2867 lb (1301 kg)
Valves/cyl.: 4
Fuel System: Caterpillar EUI
it makes 600 hp stock from cat but i have o/c ed it to 800
runs great on cetane 43. only gets 5.5 mpg. we put 1 quart of trans fulid in the tanks every 10k to keep injectors clean. ripsnort we got ya beat on fuel tanks pair of 200 gallons.
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Originally posted by Westy
And kudos to the House of Reps for approving a massive energy plan which included billions in tax breaks and subsidies to energy companies (like Exxon/Mobile). Lawd knows they needed it! Must be part of that trickle down economy thing they've been talking about for the past 4-5 years.
How DARE they pass a bill that would stretch America's gasoline supplies and make us less dependant on foreign oil supplies! Those bastards! The house wouldn't even vote approval to protect those big bad oil companies from liability lawsuits! WHy, do we really need a diverse mix of fuels? Do we really need to create jobs and spur development of cleaner burning coal and provide a new generation of nuclear reactors? Hell no! ;)
Oh, and this just in....those oil companies are gonna make money because they are in the E-N-E-R-G-Y business!
And the farmers! Those bastards are gonna make money hand over fist producing corn for methanol! ;)
Energy bill backs ethanol, not oil savings plan
Source: Copyright 2005, Reuters
Date: July 25, 2005
Byline: Tom Doggett and Chris Baltimore
WASHINGTON (Reuters) - To stretch America's gasoline supplies, the leaders of a joint Senate-House conference committee racing to finish a U.S. energy bill agreed on Monday to almost double production of the motor fuel additive ethanol to 7.5 billion gallons a year by 2012.
Rep. Joe Barton, Texas Republican and chairman of the energy bill conference committee, proposed creating an $11.4 billion fund to clean up MTBE contamination in return for shielding refiners such as Exxon Mobil Corp. from lawsuits. But the plan was roundly criticized by the oil industry, municipal water officials and key U.S. senators.
While Barton did not win liability protection for the oil companies, he was able to include draft language in the bill to require MTBE liability lawsuits to be reviewed by federal courts, setting a higher bar for such lawsuits to proceed.
White House spokesman Scott McClellan reiterated on Monday that the administration "doesn't think we need to be providing tax credits to oil companies when the price of oil is above $50 a barrel."
Bush spoke with leaders of the conference committee on Sunday and urged them to approve a final energy package this week so the full Senate and House can clear it and then send it to him to sign into law by Aug. 1.
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This is one of those subjects where both sides can be right, to some extent.
Sava....Virgil Hilts knows what he's talking about. His advice regarding hardware-related factors is spot on.
However, it doesn't take modern engine management systems as implemented in most "fuel injected" (its not really fuel injection but that's another discussion) vehicles into account. There's a capability of these systems that some refer to as "adaptive strategy". Basically, the management system is designed to push timing and fuel delivery toward what's best for performance while remaining within emissions parameters and avoiding detonation. These systems can and do allow most modern vehicles to take advantage from higher octane fuel.
Note I said "most" and "modern".
On the Pontiac V8s, yes compressions in the 10*/1 range were only 1970 and prior. My box stock 1971 TransAm with the 455HO was 8.4/1 as built, and responded really well to the .030" I took off its cylinder heads :)
culero
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Originally posted by Captain Virgil Hilts
The ragged 4.1 engine did suck, the 4.5 was not too much better, the final version, the 4.9, was decent.
The only good thing about the 4.1 was its too-soft main bearing inserts. Owners hated the fact they started experiencing crankshaft knock at 60-80K miles, but shop owners (like me, in those days ;)) loved those gravy main insert replacement jobs (its a really easy job on that chassis and with generous flat rate times).
They wised up and fixed that by the time the 4.5 came out.
culero
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Thanks,
My Volvo is a fuel injected 4 cylinder.
I just pulled out the owner's manual. It says:
(Paraphrased)
“Volvo engines require unleaded gas with an (R+M)/2 (AKI) rating of 87 or higher. This is generally equivalent to a RON of 91 or higher.
Volvo recommends (R+M)/2 of 91 for high altitudes and hot climates.”
So I’m gathering that it’s not worth bumping up the octane unless it’s really hot?
I’ve been getting only 20 mpg lately; although I’m often hauling a rowboat on the roof, that can’t help the mileage much.
I just had it tuned up a few days ago; I should see how it does now.
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eskimo, I'm not very familiar with Volvo, so I can't predict results. While the same physics govern all makes, its the sophistication of design in the management system that controls your "fuel injection" that determines whether or not your car that's rated to run acceptably on regular fuel will experience performance benefits from using premium fuel or not.
I can tell you that the vehicles the US "Big Three" built from the late 80s through the end of the 90s (at which point I made a career change and stopped remaining current on the technology) mostly were vehicles that to some extent (varied by model) would get better mileage on premium fuel than regular. Only their cheapest models used systems that wouldn't optimize performance to take advantage of the extra octane. My experience was that 1.5 to 2 MPG better at cruise speeds was typical.
But its a "YMMV" situation. I would recommend you experiment by tracking mileage carefully over a period of several tanks with both grades of fuel and compare results.
Another observation I always made based on the anecdotal evidence I saw was that engines I inspected that I knew were always run on premium fuel seemed to have much better internal cleanliness (especially in the combustion chamber but also to a lesser extent elsewhere) than vehicles that always run on regular fuel. Since I'm miserly and always stretch vehicles to their limits in terms of endurance, I see this as significant in my personal decision to use premium fuel.
You need to understand that all manufacturers have an imperative to design for, build for, and recommend usage of regular fuel as acceptable. Consumers would (with the exception of buyers of "high performance" vehicles) see the requirement of higher octane fuel, or even the admission that the vehicle won't run as well on regular as it will on premium, as a disincentive to sales.
Most people accept that engines last longer when oil change intervals are smaller than manufacturers recommend. I can certify that's true. Manufacturers recommend the least amount of maintenance that will yield barely acceptable results for the reason of minimizing expected costs of operation when selling vehicles. The fuel thingy we're discussing is relevant to that.
culero
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Culero, u still have the 1971 T/A? BTW, I'll be in Mc Allen every week day around 8am:D
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Originally posted by culero
Most people accept that engines last longer when oil change intervals are smaller than manufacturers recommend. I can certify that's true. Manufacturers recommend the least amount of maintenance that will yield barely acceptable results for the reason of minimizing expected costs of operation when selling vehicles. The fuel thingy we're discussing is relevant to that.
culero
On that note, I read a Consumer’s Report article that compared oil change frequency and engine life. They ran cars with oil changes at varying intervals (like 2,000, 3,000, 6,000 & 10,000 miles). After 100,000 miles they tore the engines apart saw no difference in wear between the 2,000 mile oil change cars and the 10,000 mile oil change cars. They suggested that the major proponents of 2k or 3k oil changes were the oil companies and oil change services. Since reading that article I change my oil about every 10,000 miles or once a year.
eskimo
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eskimo, I've seen BS in Consumer Reports so many times I quit looking at it. I have no interest in oil sales but I do have 25+ years experience doing vehicle repair. My experience tells me something different.
Frenchy no, I sold the TA in 1981, something I lived to regret (I miss it). I now drive a diesel-powered Ford Tempo.
I do know the good breakfast spots here, tho ;)
culero (my e-mail addy here works)
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So how often do you think oil should be changes?
eskimo
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"So how often do you think oil should be changes? "
IMO it depends on how hard you run the engine.
J_A_b
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I still try to change the oil every 3000-4000 miles for a few reasons.
First, it's cheap insurance. A new LS1 motor would run me at least $6000 and an oil change is $15.
Second, every time you hear a story about some guys car lasting an amazing amount of time, you'll find that he's done the 3000 mile oil change thing.
Third, having fresh oil in there isn't necessarily going to reduce overall engine wear, but chances are that at least one part of your engine is on the edge of manufacturer's specs, and it's that one part that the oil changes can keep from going bad.
Fourth, engines don't just "wear out" very often. Some part wears enough for it to break, and the amount of wear it takes to break something varies from part to part and from engine to engine.
I could go on and on, but I'll end with the observation that my Dad used to be lax with oil changes and therefore nobody was suprised when he engine threw a rod, and my firebird has 103,000 miles on it and doesn't burn ANY oil between oil changes, even on the odd occasion when I don't have time to get the oil changed and it goes up to 6000 miles between changes.
I almost forgot... Oil looks, smells, and feels different after about 3000-4000 miles. If there is a difference that I can detect in the composition and contaminant content, then I assume there is a difference in how good it is for the engine.
I'm not a purist about it and if someone wants to push the limits and delay their oil changes, then that's just fine. I'll take the cheap insurance and point-and-laugh when I hear about people who's engines die.
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Originally posted by eskimo2
On that note, I read a Consumer’s Report article that compared oil change frequency and engine life.
eskimo
Consumer Reports once rated the Corvette as extremely poor for BODY RUST. That's just one of a hundred BS ratings and rankings I've seen in Consumer Reports.
IF you want to go to 5K miles between changes, use something like Mobil 1 or Royal Purple synthetic. And a premium (not Fram or store brand) oil filter.
Mineral oil is crap after about 3500 miles. The additives are gone and the oil itself has heat breakdown.
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i really don't think you need. Only thing we buy high octane for is for our 2 stroke dirt bikes. I thing the only reason we buy that for them is because their engines need those high rpm's to actually move (10,000-12,00 ish).
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Originally posted by GtoRA2
Yeah I dont think Pontiac ever ran a 11 to 1 motor in a factory car.
Most were 10.25 and 10.50
I think the ram air IV motors were 10.75 to 1.
the 350 horse 400 from my goat that I had rebuilt was 10.5 to 1, but I had TRW forged pistons put in on the rubuilt and had them dished, so the compression was 9.65 to 1.
Ran great on 92, when it was in tune. On really hot days though it would ping a bit, so I always had some octane boost in the trunk.
They are right, unless the car states a higher octane you are just wasting you money running it.
the early 421sd's (61-62 vintage) were 11.5 to 1 they were way underated in hp as for they did the ole pic a rpm and thats what hp it had .. it was actually a 465-485 hp engine .
my '66 RA1 XS 389 also had 11 to 1 and made 426 hp
Frenchy's 455 pont should be 8.5 to 1 with 111 to 115 cc heads on it (if you found a set of "96" casting 455 heads you would have 10 to 1 ) depending on which head gasket used .028,.036 ,.044,.080 ...
now back on the 455 olds id guess its a 8 to 1 engine as for thats what most of the big blocks were in '73
oil changes .... every 2500-3500 miles depending on use and age of engine
as it gets older more fuel gets past rings and exhaust valve guides start to leak and contaminate the oil.
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you should run the high octane in the Volvo.
I've put about 150K miles on my 87 765T, and it ends up costing you any of the savings per gallon plus about 20-40% more to run the cheap stuff.
it's designed to run on 91. it won't ruin your engine from pre-detonation("knock"), since you have a knock-sensor that tells the computer when you've been a cheap-skate and it just retards your timing until the knock goes away, it protects your engine while robbing you off horse-power and gas-mileage in the process.
I get about 20-22mpg on the freeway (sometimes a little less, depending on my ability to go easy on the turbo.) with premium(usually 90 sometimes I can find 92).
about 15-16mpg if it has 87 in it.
I love the late 80's Volvo's. it's hard to beat a nice, respectable, low-key, 125mph, family car. I'm almost never late since picking this thing up used about 8 years ago.
BTW- it seems most people I talk to think that the higher octane fuels burn faster and more violently.
thats completely backward.
as octane increases the fuel burns slower and more predictably, allowing you to compress more fuel and air into the cylinder, light it sooner and be able to predict when and how fast it's gonna build pressure in the cylinder.
for better efficiency and more power you want spark before the piston reaches TDC, to the point where it's got a good solid burn as the piston starts down, but not pushing it back down before it makes it over the top.
"knock" is when the octane is to low and the burn builds to much pressure before the piston has completed it's upward part of the stroke.
also I read one post that said use injector cleaner and you don't need higher octane gas (can't remember who's it was). higher octane gas isn't about being cleaner burning. other than allowing you to build a cleaner more efficient engine with more predictable gas.
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Originally posted by eskimo2
So how often do you think oil should be changes?
eskimo
Actually, its a moving target. There are several variables I can think of:
1) Average trip duration
2) Ambient temperature conditions
3) Ratio of cruise-to-stop&go operation
4) Age/state of wear of engine
The period of engine warmup is by far the greatest problem area in terms of both engine wear and pollution of the crancase oil. Internal tolerances and oil viscosity are optimized for the engine at normal operating temperature, therefore you must reach that temperature before your lubrication system functions as well as it should. Plus, fuel mixtures and burn efficiency are likewise best when the engine is at normal temperature, your fuel burn is much more dirty both in terms of emissions and pollution of your crankcase while warming up.
So, the more a vehicle is used for short trips, the more stressed your oil will be. In addition to the factors I mentioned already, whenever you shut off your engine and allow it to cool, there is a tendency for atmospheric humidity to produce condensation inside your crankcase. The small amounts of moisture introduced to the internal environment of your engine's lubricated parts combine with by-products of the fuel combustion in the crankcase to create acidic liquid pollution of your oil, which filters simply cannot strain out (they are only good for particulate contamination).
Obviously, colder climates aggravate this.
The nature of your trips is also a factor. An engine in a cruise state at normal temperature is most efficient in terms of fuel mileage, and also in how clean its running. Vehicles running at steady cruise state pollute the air AND their oil much less than vehicles that are accelerated and decelerated frequently.
As Roscoroo correctly pointed out, engines that are older and have more wear pollute their own oil more than newer "tighter" engines.
All this makes it difficult to set a precise mileage for optimal oil change intervals.
Fleets with the best management nowadays utilize oil sampling programs that tell them what's best for their fleets based on laboratory analysis. They leave the oil in there as long as possible, by establishing through sampling just how long it meets acceptable standards.
Obviously, its pretty much impossible to get that precise with individual vehicle owners, they vary in their matchup to all the factors too much and laboratory analysis of oil samples isn't as economically feasible.
Its true that some folks, for instance folks who have engines in really good shape, who tend to start their engine, warm it up quickly, and use it for long intervals at mostly cruise speeds, may be OK with 10,000 mile oil changes. However, that's relatively few people. The more you use shorter trips to accumulate the same number of miles, the colder your environment is, the more you stop and go while on a trip, and the older your engine is, the more frequent your oil change interval should be.
My experience taught me 10-15K miles per year is average for the typical motorist, and that this mileage is achieved via 2 to 3 trips per day. In that duty cycle, I'd recommend a seasonal oil change (Spring-Summer-Fall-Winter).
Hence, the traditional rubrick of about 3K miles per oil change....which is IMO a good rule of thumb for most people.
culero
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My compliments, capt. apathy, its nice to see someone else who understands what's involved :)
eskimo, as I said I'm not very familiar with Volvos, but capt. apathy is right if they use a knock sensor as a component of their engine management system. Its there to allow use of lower octane fuel, but causes slightly less efficient operation in order to accomplish that.
culero