Hey Guys,

I just bought a 1980 corvette and had to drive it home over a course of 9 hours across the states. I was expecting terrible gas milage, something around 12-15, but actually got between 22-24 (highway). This was about a constant speed of 65.

My mustang, a V6, typically gets around 20. Any ideas on what is up with this? I should be getting way better MPG than a 30+ year V8 car. I tested my mustang on mostly highway travel, again only going 65, and I got about 20.8 when I did the math. I am not flooring it, as during the test I tried to stay under 2000 rpms for the sake of the test. But I am getting about the same gas milage as if I was driving 75-80 at 2400rpm.

I bought the car used, so it possible there is a performance tune? I don't have CAI. Is that even really a good idea without any engine mods? As far as I know, the car is completely stock.

Thanks.

 

Haha, I get nearly 30 on the highway with 3.55's.

Anyways, maybe check your plugs? I don't know what kind of mileage your car has, but I know my Ranger needs new plugs and the mpg is suffering considerably. As for a tune, many people actually seem to notice an increase in mileage with a performance tune if they manage to keep their foot out of it.

Other thoughts might be clean your intake/replace the filter, clean your throttle body, etc.

PS, 1980 Vette? Nice choice of car

 

Thanks. I have wanted one since I was kid and saw it on the road the first time.


My Mustang has 76K on it. I bought it used and have not changed the spark plugs yet. I will take a look at them and see how they are. As well as the air filter.

Clean the throttle body? That sounds like it would be a big pain. I by no mean a mechanic and although I want to learn, I don't think trying new things is a good idea for the daily driver. haha

 

Eh, you could probably pass on cleaning the TB, but why not learn? It's not difficult at all. I don't know if it would make a difference in MPG or not, but I've heard S197's tend to dirty them pretty well, and they can cause issues in idling and just running in general. As for mpg, not sure if it would have an effect.

Figured it might be worth it while you're in there.

 

I haven't noticed much of a mpg difference when I cleaned the throttle body but it runs ALOT better! No hesitation when I accelerate. Try cleaning the mass air flow sensor, that makes a little difference on mine. Search the forum for a video on how to clean the throttle body and MAF. It is actually simple.

 

My friend has a automatic v6 2010 and she gets worse mpgs than my v8 manual... I hear from a friend that Vettes are actually very good on gas. My GT usually gets about 26-28mph cruising highway at 65mph on long trips, but when I drive short trips with traffic lights and some city driving I get about 20-22mpg at average computer calculated speed or about 44mph ( I am not talking constant, just average... ) I think your car is fine, its just a combination of auto tranny and bad aerodynamics...

 

To be honest I don't think the auto should have too much to do with it or mine doesn't. I can hit the 26-28mpg average at 60 - 65mph also. I would guess like HxCGuitars and trublu07 that the TB may need a cleaning along with the MAF and plugs might need changing. You might want to look at an oil change if you haven't changed it since it was bought, Unleashedbeast has a nice write up on how certain oils can affect your mpgs.

Have any pics of the vette? C3's are my favorite generation!

 

I change the oil every 5K or so. But so far, I have not rotated the tires. Could that cause such a downgrade in MPG? There is no abnormal wear. Every time I change the oil, I inquire about rotating my tires, and they have told me it was not needed. I will do it if you guys think I need to.


Here is my first pic I took with my 1980 Corvette:

 

I don't think the tires should cause that much of a decrease in your MPGs. You could check on some fuel system cleaners, it just sounds a little odd.

Love the vette, yellow is an awsome color on them imo! Looks like it was taken care of from the pic.

 

Beautiful Vette! I used to see one just like that around the neighborhood when I was still a little kid. First car I fell in love with.