bnr517

Yesterday my wife and I drove my 75 up to the state fair which was about a 200 mile round trip. I am not complaining that I got 16.5 mpg on the trip but maybe concerned. She is powered with a ZZ4 crate engine and has a .373. Kept her around 3200 on the highway which was around 63mph. Have only owned the car a few weeks but thought it was odd to get that good of mileage. Any thoughts?

pws69

Be VERY concerned! Any Corvette that old getting more than 8 mpg MUST be going to blow up......

mobird

That is really good mileage, but I wouldn't be concerned.

I'm presuming you are implying being worried that the car is running lean and therefore using less fuel? There is a common misconception: rich and lean running have very little affect on fuel usage. Because rich and lean are just the RATIO of Air to Fuel, not the AMOUNT. Load is the controlling factor there.

But basically, you have a good problem : you are getting decent highway mileage. If you had an overdrive transmission that brought the RPMs down a bit, you could probably get into the 20's of MPG.

bnr517

Thanks mobird! Overdrive would be nice, one day maybe. Spending a fortune next week with new trailing arms and mono spring. People think boats are expensive! I can tell she runs a little rich with the smell of exhaust but I am far from mechanically inclined and just wanted some reassurance! Thanks for your input!

bnr517

pws69 that's pretty harsh. What makes you think that?

7T1vette

At 63 mph, my engine runs about 1800rpm. All that extra engine rotation is eating the fuel. I agree that 16.5 mpg with a 3.73 rear gear is pretty good. With an overdrive transmission you would be getting over 20mpg, I think.

general ike

Oh its a replacement crate engine. Absolutely no possibility of blowing up!!! Ike

cagotzmann

Just to give you a comparison.
Engine ZZ383 6 speed manual, 3.08 Rear, I get 27.8 mpg (23.4 mpg US) @ 75 MPH.

mobird

He was being sarcastic.

Rescue Rogers

I have 3.55 rear, 4 speed and spin 3500 at 80mph and get 14mpg while hot rodding around town with a 327, 365 hp motor. Your doing fine. I've been looking at a t5wc swap for the overdrive but most of the ones available around me are from mustang's. The tremec tko500 full swap is alot more pricey but everyone that's done it says they would do it again