I don't know and don't care. I usually take a short drive every Saturday, and every two weeks put in 10 gallons and a can of octane booster.
Thank God I don't have to drive this pig every day.

 

This is more like what I get. Fairly stock 91 Coupe, A4, 3.07. Get around 15 for City/Mixed driving. Have never gotten over 20 on sustained highway. And I don't care--I don't have it for the milage.

 

I just finished a roadtrip with the new 412 to PA and averaged 20mpg on the highway. Best was around 22mpg.

 

I didn't buy mine for the fuel economy either. But, when I read threads like these, it makes me question how well my engine is actually performing. I have to get some help with some scan data one of these days.

 

stock 90

about 18 city 22 hwy

 

4.10 gears, 385 rwhp, and 24-26 highway mpg

Corvettes are in fact pretty good economy cars!!!

 

15-17 around town and 25-27 Hwy

 

My 86 has a 90 motor, TPIS long tube headers and 52mm TB with TPIS chip, A4 and 3.45 gears and I average 17 city and 22 hiway. I'd get better but TPIS programmed the torque converter to lock up at 54 mph instead of 45 mph like I asked.

 

Stock '96 Lt-1 with an auto tranny and 3:45's. About 15 town, 20 highway or so.

 

15-17 around town, 27 freeway.

421 CID w/ 3.07s and an A4

 

I live in a hilly area and I usually get 22-24 mpg average through the hills. City I get around 18mpg and on the flat highway going 69mph I average around 27. Interstate at 80mph around 26. I run 89 octane and put 91 in when I can find it.
1989 Convertable 4 speed auto.

 

Stock 94
My normal driving commute habits are about 50/50 hwy city. My REAL mileage as divided out using real gas and mileage is about 20. I will get closer to 25 on a trip on a hwy.

But my indicated inst is about 25 going down the road. My average mileage as calculated by the car is about 19-20 real close to what I actual do.

 

85 4 plus 3 with 3:07 rear 23 mpg sustained highway 65 mph. 16 around town.

My last C4 was an 87 auto with 3:07 rear. I could get 27mpg highway 16 around town.

C5's with a 6 speed can get 30 mpg or better on the highway. C6 slightly lower.

 

My C4 gets 15/27 mpg. And that's with a nice mild cammed 383. When I drive it hard, it gets much worse, like 10/17 mpg.

The C5 on the other hand gets 4 cylinder Camry-like gas mileage. But its 100% stock with 2.73 gears. I get 20/30 mpg if I drive like an 80 year old grandma...

My V8 S10 gets a calculated 13 mpg from being driven hard all the time. Haven't really driven it on the highway yet. It has the old L98 from my Vette, with the exception that its carbed, is cammed (LT4 Hot Cam). Its a nice street truck and getting bad gas mileage on it is worth the fun...

 

My stock 85 gets 17 around town not sure on the interstate.
My modded 77 gets maybe 10 if I keep my foot out of it city or interstate doesn't matter. Instead of miles per gallon I like to think of it as smiles per gallon .

 

I drove to Atlanta yesterday from Orlando. Averaging ~78mph I got 26.6mpg as figured by me. The Computer showed 26.5...not bad.

 

you need to determine if the previous owner has messed up things that makes your car run inefficiently.
change the oxygen sensor, that makes a big difference.
One thing to check is the master cylinder booster adjustment that allows the brakes to drag, reducing mileage, and increasing brake wear.
Another thing to check is the wheel/brake temp after just a straight drive, and light brake pressure to bring it to a stop. if the rear brakes are hotter, your e-brake is dragging as well.
There's not a lot that can affect your gas mileage that dramatically, so it might be a bunch of little things adding up.
do all of the regular things, check tire pressures, check plugs, fuel filters, etc.
factory mufflers sometimes plug up, and because it's not a true dual exhaust,you might be running with both banks out one muffler..... mine was like that. a baffle rusted out in the muffler, and blocked the pipe.
Don't rule out a bad precat either. a restriction there only limits performance
low fuel pressure may cause the injectors to not produce a satisfactory spray pattern, and limit atomization.
vacuum leaks can make the mixture lean, causing misfire, and adding false air. your water temp will be a little high when that happens.
misfire reduces gas mileage.
.

 

This thread prompted me to do a little experiment..

I filled the tank last Friday, reset the average fuel economy readout and drove the car as conservitively as possible for the last 6 days.

Friday and Mon - Wed involved my typical work commute (25 miles, 20 of which is highway) and my lunchtime cruises.. I work on the NH seacoast so I cruise Rt.1 along the ocean at 40ish almost daily for my lunchbreak. Then I also drove the car around Saturday and Sunday doing my weekend errands etc.

I lugged around in 5th and 6th gear whenever possible and resisted the urge to nail it through the gears (which is not easy ) It's surprising how easily the car drives along at 40 -45 in 6th gear at 1000 rpms~

I ran the tank down till it said I had less than 30 miles till empty, then refilled and calculated the results.. According to my figures I averaged 25.9 mpg and the cars readout said 25.8 mpg. Gotta love that.

Now back to my normal driving habits, the average mileage is dropping

 

On a good day, sometimes 86...

 

22 Highway
18 City

15 Highway A/c On
12 City A/c On
Whats Wrong With That? But The Way Gas Prices And The Heat Of Texas A/c Is A Must.