10w30, 10w40 by accident. Valvoline by preference but it's not religious or anything.
I have 100,000 mi on dinosaur squeezings and I suspect that if I switched to synthetic I'd spring a bunch of leaks. It burns zero oil at all over 6000 miles of use, so why change something that works? The last high mileage car I tried to switch from dino to synthetic oil went from burning zero oil to burning a quart every 2000 miles plus leaking on the garage floor. Luckily switching back to dino juice "fixed" the leaks and it quit burning oil. Until I sold the car and the new owner wrecked it the first week.
I did get a bottle of slick-50 for my next oil change, but it's not like it NEEDS it...