Gage

Didn't buy it for good gas mileage, but have measured about 12 mpg in city driving. Haven't had it on the highway on a long trip to measure highway mileage yet.

I thought the fuel injection plus the 700r4 with OD would do at least 15 city. What are other 82 CFI guys getting?

MikeKey

It will, if you run ethanol free gas. I saw a decent bump running it in mine.

You could may be in need of a simple tune up or just to heavy on the pedal.

C3 4ME

No first hand knowledge, but I've seen plenty of people say their similar 82's get just over 20mpg highway, so I'd think 15 city is very doable.

2TONE82

I don't DD mine anymore but you should be getting better than 12 MPG. I see an easy 18 MPG in town but it will take me a couple of months to burn a tank of gas!

Last road trip - a couple of years ago - she turned 29 MPG, straight hwy miles. Yes, I need to get out and drive her more!

jjpish68

I have a 82 and I consistently get 19 mpg or better.

jackwabbit703

Something is definitely not right here. I had a 1983 Z28 with same engine and remember getting well over 15MPG in city and over 20MPG on highway.

Do you have stock differential or low rear end gear (3.70 or 4.11)? Having low gears in city driving will burn lot more fuel.

Gage

yes, stock 2.87.

scorpion18z

I have achieved 26 mpg on the highway with cruise control on for two hours at 75 mph burning mid-grade gasoline. I live in Florida, so it is very flat, but my 75mph was the slowest vehicle on the highway...damn near got run over a few times. It is not so good in-city driving because I keep in in 3rd gear all the time so it won't bog down. I can't say I don't goose it every now and then (to blow the carbon out...LOL), but I keep it at speed limits for the most part. Stock CFI engine with no added speed tricks and she runs great. Idles also. Summer is upon us now and I will be adding the HVAC load, which will proably drop the MPG down in the city. My DD is a 86 el Camino that has a few speed tricks and it gets damn near nothing in the city (12 mpg), but a respectable 21 mph on highway.

pakrat12

I have the original window sticker from my 82 and it states EPA Fuel Economy Rating of 15. That is about what I'm getting for mostly city mileage, and I also keep it in 3rd gear for city driving...the only mod to mine is CC true duals with no cat.

7T1vette

Is your ECM system still operational and functioning properly? Does your check engine light come ON when starting the car but go OFF once the engine is started? If the CEL does not light when starting the car, the computer could be malfunctioning and default to a "baseline" program that is intentionally set to the 'rich' side (to protect the engine).

If ECM appears to be working properly, you may have a defective O2 sensor that is still sending "OK" signals. It can happen.

terry82

21 highway mpg .if your cat is factory it is pluged .

Gage

cat was removed and replaced with a test pipe. My CEL comes on at startup and then goes out like it is supposed to. Cars seems to run fine, spark plugs are new. Headscratcher here.

Could removing the cat cause the O2 sensor to read wrong which is causing too much fuel to be dumped in?

74 LS4-454

I also get 19 or better, close to 21 on the highway without stop & go traffic and without keeping my foot out of it.....
Have had it as high as 25 mpg on the first day I bought it
And it feels smoother through out the rpm range, now that I removed the cold air door flap.......

74 LS4-454

It could be a number of factors.....sounds like you just purchased your 82!!!
Have you done anything to it yet? such as:
...a tune-up....I see your plugs are new, but how about the cap, rotor, and have you checked the ignition module out? your plug wires, air filters, etc., etc.
...replace the fuel filter....etc...etc...
...what do you idle at in "D" and in "P" or "N"?


I also have the cat removed on my 82 and replaced with a true dual exhaust with a H-Pipe in between and the oxygen sensor connected, and it doesn't throw any codes or promote any problems.

terry82

removing of the cat does not hurt anything .removing to much back pressure will throw a code .if that happens you need to go to a heated o2 sensor .I would change the 02 sensor .that way you know what you have .then I would check my injector spray .check plugs to see how they are burning .if they are black ,then you are burning rich .change o2 sensor plugs and the coolant sensor up front by the water pump.

Arkyvette

Hopefully I get at least 200 miles on a tank...my gauge doesn't work and I'm making a highway trip today. So far I'm impressed by the fuel consumption of this car. Way better than a 3 speed carb car.

David Mc

Bump your timing up a couple degrees and recheck your fuel mileage

Wrecked82

I returned my timing down and it runs smoother and gets better mileage. I always understood you would loose some mileage and run hotter with advanced timing but maybe gain some performance. Know the engine idles smoother, exhaust sounds smoother, etc. at specified timing.

Gage

checked for stored codes, nothing but good ole code 12!!!


Could O2,coolant temp sensors be bad without throwing a code?

When I bought the car I did notice a small amount of black soot on the bottom of the back bumper just above each tailpipe. I cleaned it off about 2 wks ago and its still clean.

David Mc

I think your info is in error.

The factory specifications, whether ignition timing or cam timing, have been retarded to help with NOx emissions. This lowers cylinder pressures, performance and fuel economy. Of course cylinder pressures that are too high increase chances of detonation so you have to careful with changes. As the timing chain wears and stretches, increasing the advance a couple degrees should give noticeable improvement.