ive been working on my 280's mechanical gremlins for a few weeks now and have noticed a descent jump im mpg. was getting around 10 mpg when i bought it, and am currently getting 16. she's still running rather rich so im hoping i can get in the mid to upper 20's out of her. whats the average for these cars, how far can i push it?

By all means, i'm no expert - But i think the best you can hope for 25mpg (highway). Even if you are getting 20, you are doing pretty well.

I get about 18 - 20 MPG in my 280 - and it's EFI. I'm due to have a valve adjustment, but other than that - i'm not sure what I can do to improve the MPG.

On a side note, I find it very hard to get an accurate MPG reading when I drive the Z since my foot becomes very heavy when i'm in it!

Edited March 22, 200916 yr by mikewags

My 78 gets 19-20 city, 24-26 hwy.

With my stock 3.54 FDR, '78 5-speed, stock tire OD, 10:1CR, AZC header, stock cam, and tiny stock exhaust, I get about 23 mixed and 26 hwy on 93 octane gas. Before driving it this spring, I will install my Web 0.450"/260° camshaft. I'm interested to see what effect it will have on fuel economy.

If you go by the dealer paper work from the late 70's you end up with

16 City

27 Hwy

EPA fuel economy ratings in the 1970's were about as accurate as SAE Gross horsepower ratings. The window sticker didn't really predict real world fuel mileage. Today's method's are much more accurate for the way people really drive.

Couple that with the fact that today's fuels are not as conducive to higher mpg as fuels of the 70's.