seasonedgrandsport

I have 52,000 miles on my car, clean and replaced factory air filter everything is stock in the car, using 93 octane gas. Gas mileage on the highway at highway speeds plus 10 seems to stay around 22.5 - 22.9 running Michelin RF @ 34-35 PSI hot.
This is a 6 speed manual car; seems I should be getting better mileage??

rjken1969

I average 16 MPG in my 2012 CE GS M6. Nearly 23 seems doesn't seem bad to me.

MYCoupe

Not sure what speeds you're traveling at as 10 over is not very indicative of actual speed not knowing the speed limit. All that aside my GS doesn't get great gas mileage either, but does seem better than yours. I think the wider tires add to the rolling resistance and are somewhat to blame. At 65 MPH the best I can do is 26-27 MPG. By the way I'm running Michelin PSS ZP and my car is a 6-speed manual as well.

seasonedgrandsport

Thank you, I have Michelin PS 2'S with about 22,000 Mi. soon to be replaced. guess my mileage is about normal.

old motorhead

You're heavier than just about any other C6. In 6th gear, you're turning your engine faster than a base model (different O/D ratio). And the bigger/heavier tires don't help any compared to a base model.

My previous Vette was a 2013 GS M6. It would get low to mid 20's mpg on the highway. Current 2013 M6 narrow body gets mid to upper 20's doing the same work.

Nothing "wrong" with your Vette. Worry about something else. It kinda is what it is.

Suns_PSD

A lot of that must be in the wind resistance cause I have a Z51 NB, but with wide tires F&R (275 & 345s), with 4.11 gears, and it'll get upper 20s pretty easily on a highway trip. It'll get 22-23 when on E-85 as it's set up flexfuel.

seasonedgrandsport

Thanks for your reply, I know this is a heavier car and the wide tires make a difference, guess I'm happy / a friend with a 08 C6 narrow body 6 speed with headers and more open exhaust gets 26-27 on the same trips. Thanks again

Olsarge

On a 468 miles trip I set the cruise at 75 mph on my '12 GS A6 and got 25.9 mpg. I was very happy. My 4X4 Silverado gets 12 mpg on it's best day.