im getting 14 mpg on a totally stock m6 94 z28. i just picked up the car at the beginning of this year and have been in the process of changing all the fluids and hopefully the mileage will get better after i get new plugs/wires in. car has 174k km's on it. this is with 95% "spirited" city driving

 

Our cars are extremely sensitive to driving style. With all that power on tap, you can either get good gas milage by babying it, or very crappy milage if you tend to mostly quick city driving.

The 6th gear in the M6's really help to bring up the mpg on the highway. If I did strictly city driving, I bet my milage would be about 16-17 mpg, so I wouldn't feel bad if you are getting about 15 or so.

It's a good idea to run a good fuel system cleaner through the system every few months. I really like the Valvoline brand fuel system cleaner. It's in a silver bottle at Walmart. About $3-$4. It's one of the few cleaners that I have definately felt it work. Smoother idle and smoother acceleration if you haven't used it in a while (4000+ miles)

Dan

 

I went from 12/18 city/hwy to 23/28 after a complete tuneup, cam, and T-56 conversion one weekend...dont even have roller rocker arms installed yet! record low mileage is 16 city if I dog it everywhere....

be interesting to see how these numbers change with a cc306...

 

I've kept a running total since I bought the car in 2000 and it's long time average is 19.1 in mixed driving. It is a pretty much stock M6.

 

1996 LT1... bare bones stock w/ 128,000 miles... still getting 25mpg average city/hwy mix. Not bad either, since I LOVE acceleration torque and tend to be heavy footed!

 

95 Z A4 with 3.23's normal driving 22-25mpg best was 29 with all highway.