Unusual gas mileage situation

[Reschke]

LMAO... 

No such thing in Wisconsin...it's cross wind or head wind.

Well we know there aren't any big monster hills in Wisconsin...at least in the part I have been to down around Milwaukee, Kenosha and Racine...unless you count the cross overs for the county roads that are lettered after the alphabet...

[Widewing]

I don't pay much attention to EPA mileage ratings, as they are usually estimates.

My 2008 Wrangler routinely gets 25+ mpg when cruising at 65 mph (using cruise control). On one trip to Montauk, I averaged over 28 mpg, boosted by a steady 15 mph tail wind.

Two things contribute to this. First, I'm running 3.87 gears instead of the 4.10 gears. Second, I get my best mileage running on my Goodyears. If I switch over to my off road 33" Hankook Mud/Terrains, I drop 2 mpg. Checking the Tire Rack's tests of All Terrain tires, it confirmed that the Goodyears have a lower rolling resistance than anything else in the same class. Tire rack reported a 1 to 2 MPG increase on every vehicle they tested them on. I run them at 38 to 40 psi, which only reduces the resistance to rolling. Just remember that rolling resistance is a much greater factor at highway speeds than at low speed around town. I see very little difference between the two types in local driving.. IE: 17 mpg.

Since the Goodyears work much better in snow than the unsiped Mud Terrains, they are the better winter tire. Inasmuch as both work well in deep beach sand, I only swap out to the Hankooks for trail riding or when mud will be commonly encountered.

As to getting better mileage in any vehicle... A proper state of tune is required. Moderately worn tires can generate better mileage as tread wiggle in new tires generates more resistance and greater heat build-up. Badly worn tires change the final drive ratio very slightly, enough to offset lesser tread wiggle heat build-up. It's a wash.

Your vehicle's alignment is important. Any slip angle on the tires generates resistance and heat, cutting into your mileage.

Use cruise control on the highway. It's more consistent than most drivers. If you're not using that luggage rack, ski rack or anything else similar, remove it. Cleaning up the aerodynamics will always reap a mileage improvement. Some aftermarket aero items can actually hurt mileage. Wings and big spoilers add down force, but they can also increase drag by leaps and bounds.

Slightly over-inflating the tires will not seriously impact tread wear and you can gain up to 5% on your mileage (2 or 3 % is more likely).

High mileage engines often get better mileage as internal friction is minimal. Ditto for high mileage manual transmissions and differentials.

Almost any vehicle can exceed EPA rating with careful driving and attention to details.


My regards,

Widewing

[Captain Virgil Hilts]

A looser or worn engine, so long as it is not using oil or suffering from blow by, will have a lot less friction with no real penalty. Further, it will have likely built up some deposits in the combustion chamber and on the piston, increasing the compression ratio. This will increase power slightly and improve fuel mileage somewhat. It often takes several thousand miles for a switch to synthetic oil to yield the end result. In other words, it may take a while to get the full effect.

[phatzo]

I find the fuel system cleaner/octane boost gets me an extra 20 to 30 klm out of a tank in my bike and has a residual effect over the next few tanks. For the record I have recieved best results from Nulon Pro Strength (not for street use, lol)

[gyrene81]

Wings and big spoilers add down force, but they can also increase drag by leaps and bounds.

Slightly over-inflating the tires will not seriously impact tread wear and you can gain up to 5% on your mileage (2 or 3 % is more likely).

Almost any vehicle can exceed EPA rating with careful driving and attention to details.


My regards,

Widewing

Good stuff Widewing...takes a truel auto enthusiast to actually learn stuff about their vehicles.

I have a spoiler on the back of my car...  Factory install...

If you're going to "over inflate" (and I know you know this) be very careful...large diameter wide tread off-road tires can tolerate over inflation of 5 psi or more, much better than standard passenger car all season radials and performance tires...as a generality the standard passenger car tire is only 4 ply...performance tires will be 4 to 6 ply...off road/truck tires tend to be 6 to 8 ply...the thicker the tread ply the more tolerant of deviations in tire pressure.

Personally, while I managed a tire shop, I learned from several manufacturer reps that for standard all season passenger car tires on front wheel drive vehicles, 1 to 3 psi of over inflation on the front (depending on car weight, tire diameter and tread width) can improve handling and mileage...but, the warranty is void if they find out you have run your tires like that.

There is so much information out there that the average consumer has no clue about..it's mind boggling.

For me...careful driving consists of getting from point A to point B without any collisions...that's as careful as I get. 

High mileage engines often get better mileage as internal friction is minimal. Ditto for high mileage manual transmissions and differentials.

Now this is where I got confused...with the old V-8s and straight 6s (pre-1980)...an engine with 100,00 on it without a rebuild almost always got worse gas mileage than a fresh build...rings, valves, lifters, points, plugs...loss of compression, loss of intake pressure, collapsed lifters, carbon buildup, etc...less friction or not, performance was a steady downward spiral until the engine just gave up starting at about 40 thousand miles...(less if you were always pedal to the metal)...


I'm just wondering at what point this little Neon 4 banger is going to start showing that trend or am I to be driving down the road one day and it will just die never to be revived? Scary thought.


Phatzo...is that Nulon stuff safe for fuel injectors?

[phatzo]

Phatzo...is that Nulon stuff safe for fuel injectors?

as long as they are not plastic, DO NOT put anything like this in a vehicle with plastic injectors as a lot of modern motorcycles have. But it works well the  acks Kia.

[Widewing]

Good stuff Widewing...takes a truel auto enthusiast to actually learn stuff about their vehicles.

I have a spoiler on the back of my car...  Factory install...

If you're going to "over inflate" (and I know you know this) be very careful...large diameter wide tread off-road tires can tolerate over inflation of 5 psi or more, much better than standard passenger car all season radials and performance tires...as a generality the standard passenger car tire is only 4 ply...performance tires will be 4 to 6 ply...off road/truck tires tend to be 6 to 8 ply...the thicker the tread ply the more tolerant of deviations in tire pressure.

Personally, while I managed a tire shop, I learned from several manufacturer reps that for standard all season passenger car tires on front wheel drive vehicles, 1 to 3 psi of over inflation on the front (depending on car weight, tire diameter and tread width) can improve handling and mileage...but, the warranty is void if they find out you have run your tires like that.

There is so much information out there that the average consumer has no clue about..it's mind boggling.

For me...careful driving consists of getting from point A to point B without any collisions...that's as careful as I get. 

Tires are a topic where a little bit of knowledge can go a long way to getting more from your vehicle.

I mentioned that I have two sets of tires for my '08 Jeep. This Wrangler is an S24 optioned X model. The S24 option package for 2008 included many upgrades, including Rubicon springs and shocks, 17" wheels and 255/75-17 AT type tires. For 2009, Jeep eliminated the Heavy Duty (IE: Rubicon) suspension as an option on the X model. The standard tires are 32" Goodyear Wrangler SR-A All Terrains on factory 17" alloys. These are very good tires for general use. Adequate for light to moderate off road use, superior in snow. They are quiet on the highway and get better fuel mileage and are much better in snow than the Goodrich KM Mud/Terrains that are standard on the Rubicon. My X has been upgraded in several areas, mostly by adding extra armor (rock sliders, additional skid plates) and the factory Trak-Loc axle package.

For more challenging off road adventures, I purchased a set of powder coated steel wheels and a set of 33" Hankook Dynapro Mud/Terrains. Steel wheels are a better choice as they flex a bit, rather than just crack like aluminum wheels tend to. Unsprung weight is not an issue, as it can be for performance road cars. If you're going to do some serious off road craziness, invest in high-strength steel wheels.

33" inch tires don't generally require bead-locker wheels, unless you plan to run ridiculously low tire pressures (a bad idea anyway). For 35" tires,  bead-lockers are a good idea. For 37" rubber and larger, bead-lockers are essential for safety. At low tire pressures, you won't pop a bead and at highway speeds, they will keep the tire on the wheel should the tire fail. I used bead-locker wheels on my lifted '63 CJ-5, fitted with 36" Cepek rubber. Aside from welding in a full roll cage, the bead-lockers where the best safety investment I made. My '92 YJ Wrangler was far more conservative, running a 1.5" lift with 30" Goodrich rubber. These were my weekend toys, with the YJ spending many days on the ocean beaches.

Beginning back in 1972, I was involved in road racing and SCCA Solo events for 30 years, on and off. I owned a '58 Alfa Romeo and several MGs back then. You learn a great deal about tires doing this. This knowledge has been carried over to my street cars. One thing about Solo events (gymkhanas, autocross and time trials) is that you will never have any time to build heat into your tires. If running street tires (required in many competition classes), you buy tires that work well cold. You get the tread shaved and you learn that running higher pressures than normal is essential for maximum grip when cold. When road racing, you will have warm-up/pace laps to build heat into the tires and get the pressures up to where they perform better. This is not the case in Solo events, where you wait in line to run.

One last point about running tires slightly over recommended pressures. Check pressure when the tires are warm, not cold. Most street tires will see a 2 to 5 psi increase as they heat up, even in winter (although the baseline pressure will drop 5 psi or more at very cold temperatures). Drive the car for at least 10 minutes before checking pressures, longer is better. Adjust the pressure while still hot.

Here's why: If the recommended pressure is 29 psi, running 32 psi will provide crisper turn-in and less slop in transitions. However, if you set the pressure at 32 psi on cold tires, you will end up with as much as 37 psi when they heat up. This will actually reduce your contact patch with the road and they car will feel darty, sometimes hunting around the lane. It also adds considerable stress to the tire carcass, particularly the sidewalls, which are often only 1 ply, maybe two at best. So, you decrease handling, increase risk of a sudden failure and you will wear out the center of tread quite quickly. So, remember, try to adjust pressures when tires are warm. If that is not possible, set the pressure about 2 psi lower than desired at normal operating temperature, and adjust from there when you can check them after driving for a bit.


My regards,

Widewing

[CAP1]

Here's why: If the recommended pressure is 29 psi, running 32 psi will provide crisper turn-in and less slop in transitions. However, if you set the pressure at 32 psi on cold tires, you will end up with as much as 37 psi when they heat up. This will actually reduce your contact patch with the road and they car will feel darty, sometimes hunting around the lane. It also adds considerable stress to the tire carcass, particularly the sidewalls, which are often only 1 ply, maybe two at best. So, you decrease handling, increase risk of a sudden failure and you will wear out the center of tread quite quickly. So, remember, try to adjust pressures when tires are warm. If that is not possible, set the pressure about 2 psi lower than desired at normal operating temperature, and adjust from there when you can check them after driving for a bit.


My regards,

Widewing

I RUN 35 psi on my geo prism, and 40 psi on my dodge dakota. on the prism, it only yielded 1 or 2 mpg. on the dakota, it yielded almost 4 mpg in optimal conditions on the highway. so far, they've not exhibited any weird or unusual wear.
 i never checked them hot though....which i will do now, as i'm curious.

i did used to check the pressure difference on our drag slicks all the time on the camaro. we ran 7.5psi in them. after a full run, which obviously included a burnout to heat em, they were usually only around 8.1 or 8.2 psi.

 my drag radials on my mustang, i ran 19 cold, and they only went to 20 after a run.

 i'll update on the geo tonight, as i'll check here at the shop before i leave, then again when i get home....which is 8 miles of partial highway, then stop n go driving........

 

[superpug1]

some cars can get better than advertised milage to. My friend has a mazda 3 with the 2L and 4 speed auto. Its only advertised as getting 30 on the Hwy, only time she got that bad a milage was through a crazy rain storm on a back road with the roads covered in water. Usually she averages about 36 mpg...