My 01 Firehawk I just sold got 19mpg city/26 on the highway...mods included a 12 bolt w/4.10 gears, LT Dynomax w/deleted cats, 6 speed. And I have a heavy foot.

 

I just took a road trip in my '02 SS M6 convertible with the top down and I kept my foot out of it to see what kind of mileage I would get. This was open road driving 60-70 MPH, the round trip was 190 miles and I needed just over 10 gallons to top the tank off. I have no codes set and I just had a computer tune. I have an SLP lid, smooth bellows, free ram air, VHP valve train, the least restrictive muffler option from GM, and 3.42's. I keep the tires inflated at 30 PSI cold. We do have oxygenated gas around here, but I can't believe it would cause such a disparity in mileage. I didn't buy the car for fuel economy, but I don't see why my mileage would be so much less than some of the rest of you, particularly the A4's. Why your mileage would be 35-40% better than mine doesn't make sense.

 

240-260 per tank...mix of city/highway and a good amount of fun when the conditions allow for it :-)

 

Maybe the top down aerodynamics and your crappy gas (oxygen) hurt it that much? I don't know, but ~19 mpg cruising down the interstate in an M6 isn't very good. Something is up with that.....I can get better than that in my cammed A4, on ET streets.

 

Mine has had the same fuel consumption rate since I got it. I drove it 900 miles to get it home after I bought it and I didn't really see any big difference between the gas that is oxygenated and the gas that isn't. I filled up every 160-180 miles. I thought it wasn't very good when I saw the posts here, but it hasn't changed with the few mods I've done and the tune done just recently. Plugs look fine, wires are new, and the fuel trims were a little rich before the tune, but my tuner said all the factory settings are rich. It runs good and there aren't any codes nor have there been since I got it. I'm going to get an underdrive pulley in a few weeks and I'm also going to do a dyno run/tune this summer so I'll ask my tuner about it. As I said, fuel economy wasn't the thing that caused me to buy an LS1 SS, but I do hate to think I'm putting any more money in the pockets of the religious finatic US-hating oil producing nations than I have to.

 

oxygenated crappy gas i believe does affect some ls1's bigtime it seems. I know my cars gas mileage dropped off bigtime after using california style gas up here, and i blew up a cat in the process and im still getting 10mpg! nothings changed, no codes, just different gas!!! I know another guy with the same problem, used 93 exclusively on the east coast, moved to cali and his mileage dropped to 11mpg and the gm dealer couldnt find crap wrong.

 

I did quite a bit of highway driving this tank. I'm up to around 220 miles with a 1/4 tank left. Even when the "check gauges" light comes on due to the gas level I still have around 3-3.5 gallons left when it hits E. I'm averaging around 19mpg....this tank due to the highway driving is gonna be well over that.

Not bad for an A4

 

19 w/ mods in sig.

 

i get like 14

 

I just drove from MO to CA (1600 miles) and got 30.12 mpg, 01' 6-speed. Which means with a 16.5 gallon tank I could have gotten 496.98 miles to the tank, but I dont think I ever let it go past 375ish miles to the tank, better to be safe than sorry and run out of gas in the middle of no where.

 

I get about 220-260 dependent on how much screwing around. I'd get a locking gas cap and check for a whole in the tank LOL

But cap I would check my buddies neighbor was stealing his gas for montchs before he figured it out LOL

 

I get around 15 in town and 26 on the highway in my 01 Cammed M6. However, when it was stock I could get 29 to 30 on the highway. My question to you M6 cammed cars, do you get better mileage in 5th or 6th? I'm afraid with more overlap that the car is wasting a lot of gas cruising at 1700 rpm.

 

I run Ultra 94 Sunoco. If I run the car in 3rd gear in town (25 to 30 mph), 4th gear on the highway (55 to 60mph), and 5th gear interstate (70 to 85mph) I average 16.5 to 18.5 depending on how many 100+ runs I do. Lately, I have been running 4th gear in town (25 to 30mph), 5th gear on the highway (55 to 65mph), and 6th on the interstate (70 to 80 mph with cruise set mostly) to get a best of 22 mpg. I shift on average at 2000 to 2500 rpm sometimes skipping gears. Also I get around 230 to 270 a tank with a 13 to 13.5 fill up.

 

My 02 gets 21 MPG .