General LSX Automobile Discussion - Interesting Gas Mileage Comparison Between My F-Bodies

I had the '99 Trans Am (A4 most of it's time with me with a few different stalls then a M6 swap) for five years, had a '96 WS6 M6 briefly, and now I've had the '00 SS M6 for a few weeks. I find the gas mileage and fuel range comparisons to be interesting...

'99 Trans Am (A4/2.73/3200 stall) - I drove this thing like I stole it. It was my car just before I turned 18 and I had it for a while after. There wasn't a single time I drove it and then parked it without going WOT at least once, often much more. Always cruising 5-10mph over the speed limit, always accelerating fast, etc. It was pretty rock solid in the mileage tank after tank. 18mpg city, 22mpg mixed, 26mpg highway like clockwork.

'99 Trans Am (A4/3.42/4000 stall) - Once the big stall and gears when in I really didn't drive it as much, but I still gave it my fair share of hell when I did take it out. It wasn't a daily at this point so I never cared to consistently record gas mileage, but it went down a decent bit, but not horribly. I seem to remember clocking 18mpg in mixed driving, so I lost about 4mpg on average.

'99 Trans Am (M6/3.42) - Gas mileage never got much better after the M6 swap surprisingly. It would go about 220 miles to a tank during mixed driving with spirited runs pretty often, which puzzled me, because I thought the mileage and range would have exceeded even the A4/2.73 combo, but it didn't.

'96 LT1 WS6 (M6/3.42) - This car was a A4 to M6 swap also. It got absolutely horrible mileage for some reason. Never saw 200 miles to a tank. Around 170 miles I was looking for the nearest gas station.

'00 SS (M6/3.42) - I'm daily driving a F-Body again, and the SS is clocking low 20s in mpg pretty consistently and getting around 250-260 miles out of a tank before my Check Gauges light comes on, which I suppose is what is to be expected in mixed driving. I drive it fairly easy, often times never going WOT or getting near redline, and usually keeping it below 2000 RPM while going to and from work. If I get happy with the gas along with mixed driving it'll drop down into the 17-19mpg range, but happy on the gas now is a lot different than when I had the '99 Trans Am. I'll maybe do a single gear pull instead of running through the first three up to 100mph.

What I find odd about this is that going way back to my original F-Body, the '99 Trans Am when it had a 3200 stall in it and I drove it like a madman, it was still getting equal to better gas mileage than any of the 6-speed setups I've had, including the SS which is basically stock (lid + catback). I don't get how a car I drove so hard with an auto is beating out 6-speed car in mileage under the same type of driving conditions (except maybe now with the ethanol in the gas we have around here it's hurting me some compared to what it used to be).

What are you guys seeing for your range before the Check Gauges light comes on, or any other markers you use (I rarely get down to the light coming on as I usually fill up after half a tank, but on the SS so far the best I've gotten is 180 miles @ half a tank, with it usually being around 150 miles for half a tank)?

That's weird... I drove from Milwaukee back to Louisville (Around 400 miles one way) and the car only has a lid and flowmasters on it (that I know of). I was getting at least 200 per half tank. But this was with VERY easy driving. I hardly ever got on it since I had just bought the car. Now, I drive mainly in the city and am going probably 5-15 miles a day and a half tank is lasting me a week. I haven't completely kept track of the mileage as of yet, but I definitely notice that if I get on it in the car my gas is just chugged...

i dont think 98s had check gauges light come on for gas but i currently get about 150 to a half a tank

I have had 2 stalled A4's (3200,3400) and neither one have ever gotten over 14 mpg in town. I dont know where people are getting 18+ with stalled autos. I drive very easy around town also.

My old M6 LT1 'bird got consistantly over 30MPG when traveling cross country on the highway. Around town it was low to mid 20s and it had a check engine light on 90% of the time. Hence the reason I no longer have an M6 LT1.

i have an 00 Z28 and with a lid/catback i got 28.5 mpg, and that was with at least two runs up over 110mph. The guy i got it from said he got 30 or 31 once. Something isnt right if you are getting that low with an M6 cause now with a FAST 90 intake, True Duals i still get great gas mileage if i can stay out of it.

I bought my car pretty much brand new. When it was box stock, the best I ever pulled was right around 20mpg. This is with an A4/3.23's.

I put an ASA cam and 3600 stall in and kept the 3.23 gears. Highway mileage dropped to about 18 and mixed dropped to 15-16mpg.

I swapped out the drivetrain to a t56 and 9" rearend with 4.56 gears. Motor and tune were left as they were with the A4/10bolt/3.23. Mileage went to 18-19 mixed driving and I knocked down 24mpg on '08 power tour. That's 4mpg better than it got stone stock as an A4 car. M6 trans = gas mileage queens!!!:hail:

Current setup gets about ~12mpg....the gas gauge needle moves below the Full mark by the time I pull out of the gas station. :lol:

with mods in my sig.. mixed driving with the occasional WOT, i get about 19-20 mixed. Cannot complain as i have 410s. however, the m6 more then makes up for it

When I first got my car it was bone stock. On the way home NJ - NH I clocked 325 miles to a full tank.

After my Cam and bolt ons I see about 250 or so miles to the tank. Even if I constantly beat the hell out of it, I always get atleast 200 miles to the tank

Mine was 400 miles per tank - all highway when I got it in near stock form (30+ mpg)

After the cam, I get 200 miles city, and never over 300 anymore, even all highway.

I've found that the A4/2.73 combos get some pretty impressive mileage. Mine, with a stock stall, does between 17-19 in the city, 24 mixed, and 26+ straight highway. And that's with some very aggressive driving too.

My 3500 stall/3.23 geared/cammed car never did better than 14 in the city, usually 12. I have no clue what it did on the highway. I drove it like a race car every time it moved.

My stock geared M6 with lid and catback got 22-24 mpg mixed with my gunning it at every light.

I did around 27 one time, but that was using 6th gear, and it bogged a lot.

I think the gas quality has gone down drastically since you first got your TA Josh...
All cars are different. I average 20 city in the GTO, and best of just 23 highway. Which i'm happy with I guess for a GTO.

My cars have all gotten weird MPG. 98 cammed stalled z28 got best of 20 highway. it got about 15 city. I had a bolt on trans am M6 that got 30! driving back and forth to college on 2 lane 55mph roads. I had a cammed m6 T/a that got 24 highway and 20 city. I had an a4 01 z28 that got 26 on the power tour. its all a toss up

My Z seems to get 18-19 mixed driving and that's with the 6.0 I was hoping for better, but I it looks like that's about all it's going to do. I haven't made any all highway runs with it yet. Maybe I'll see something in the 23-24 range. Still beats the heck out of my 454 Malibu!

i had a 2001 automatic v6 camaro 3.42 rear and got about 20 mpg with city/highway mix.
then with my 1999 automatic SS with 3.23 rear i was averaging slightly higher at about 21 mpg. of course, i used to have my foot to the floor with the v6 and sprayed nitrous often. then again with the SS, i also had my foot to the floor, but not nearly as often even though i was going a little faster and passing cars on the highway with sprints that were about 30mph faster.

now with the 3600 stall, i'm down to about 15-17mpg. with the deadspots gone due to the stall, i have my shit screaming down the road wherever it goes. if i kept my foot out of it, i'm sure i could squeeze a consistent 17-18mpg out of it.

I have had 2 stalled A4's (3200,3400) and neither one have ever gotten over 14 mpg in town. I dont know where people are getting 18+ with stalled autos. I drive very easy around town also.

i agree. i have no idea how some guys can claim a stall doesn't really affect gas mileage unless someone's pushing their car up until they reach tcc lockup speed.

When my car just hand a lid and catback I would get right around 24 mpg mixed with 2.73's. Best tank I ever got out of it was 26 mpg. Started adding bolt on's and got a tune and it dropped to around 22 mpg. And after I added 3.73 gears, I now get 20 mpg no matter how hard or easy I drive the thing.

95 V6 A4 Camaro completely stock got 14-15mpg with easy driving city. The 99 WS6 M6 got 18mpg first tank with several 100+mph runs and several WOT moments nearly every day along with a little highway driving. Funny how that works. Are there any techniques to saving gas with an M6? Also the car smokes a little so I am sure it can be better with a tune.

Definitely alot better than the 4 MPG with the 1980. Jesus Christ that car would suck some gas. Took a quarter tank to get to school and back one day.

I squeezed 27.5 ish mpg out of my 2002 camaro z28 automatic with cruise control.
Mind you this was mostly highway but with a little traffic here and there. Oh and this was the first day after I got the new FLT level 3 transmission install with the new 3200 yank stall,trans cooler, and my old hooker cat-back exhaust.

Not bad for a v8. :cool:

95 V6 A4 Camaro completely stock got 14-15mpg with easy driving city. The 99 WS6 M6 got 18mpg first tank with several 100+mph runs and several WOT moments nearly every day along with a little highway driving. Funny how that works. Are there any techniques to saving gas with an M6? Also the car smokes a little so I am sure it can be better with a tune.

Definitely alot better than the 4 MPG with the 1980. Jesus Christ that car would suck some gas. Took a quarter tank to get to school and back one day.

shift right at 2 grand every shift. and anywhere over 45 try to stick it in 6th. I still do that with my ms3 gto. I actually stuff it in 6th if i'm going 40 cruising through town. I'm amazed how I can lug it around with a big cam, but i've messed with the tune a LOT.

fwiw my 98 z a4 before I put a cam in, got 24 highway with a 2800 stall that didnt want to lock..on my way back from S/C when I bought it. it never did that good again after the cam, even when I tuned the stall

I have an M6 and just the basic mods in my signature, plus a tune and I only get 16 mpg (85% highway mileage each tank). I have been shifting at 2K RPM and got it up to 16.2 mpg this week!!! WOOT!!!

I thought when I put the SLP lid on along with headers and a borla catback I might get up to 18mpg due to a more free flowing exhaust and air intake. Such is life I guess...

Oh, and the car only has 68K on it in 9 years so it is not like it is worn out. I have a SES light on, but it is due to the fuel sender being bad in my tank. Any chance tht forces the car into a limp mood or anything? I just had the tune done two weeks ago when the exhaust was put on, so everything was looking good on the read outs.

Little late on this but... having an M6 T/A, lid, SLP MAF, no tune, no other mods, and 109K on the clock running about 20/80 on City/Highway I get between 25-27 mpg. I typically do what ZTwentyAteU mentioned which is 2K shifts and ~45-50 hit 6th. I, on the other hand, only use 2/4/6th gear normally. Too lazy to disable skipshift and 1st seems too short for me anyway. Straight highway from Knoxville to Baltimore I was getting between 29.5-30 running ~70-75. People say that these cars like that speed...

1998 Z28 M6, (mods in sig), 136k miles. I average around 20mpg, but on road trips I get around 28 with 4.10 gears. Once, while driving from Roanoke VA to Montgomery AL I got like 34 mpg, but that was a true scientific run :D I had HPTuners open in the seat beside me with a custom MPG PID, I tailgaited semi trucks (thanks MythBusters), and put it in Neutral going down hill. You would be surprised how much a 1% throttle difference can make in fuel economy. When you go down a hill in neutral at 80mph then you really are getting like 100mpg. Anyone that's familiar with the stretch between the top of the mountain in Chatanooga and I 59 ought to remember that long gradual down hill grade that lasts for like 5 miles. If you can travel that whole distance and only spend the fuel to make your car idle then you can really affect the average MPG.

My 1996 Z, with the same 4.10 gears, EWP, UDP, shorties, CAI, "airfoil", Hypertech :rotflmao:, LT4 KM, Borla, would consistantly knock down 30mpg on the highway.

Speed seems to be the biggest mileage killer, as it takes more throttle percentage (thus deeper MAP cells), from my observation. RPM has less of an effect on MPG than you would think...

Before my cam I got 30 a few times, with 4.10's! The cam lowered it to about 28. Although I did get 29 this summer on the one trip I took it on. And I got on it a few times. I was impressed

i dont think 98s had check gauges light come on for gas but i currently get about 150 to a half a tank

MY 99 with similar mods gets about that range too.

With an m6 swap and 3.23 gears I get about 250 miles a tank, its really not all that different from the automatic, except that its alot more fun to drive now.

My 98 a4 ta with 3.23s gets around right at 21 mpg with lid and lt's untuned. Just took a recent road trip and got around 24 mpg, but I drive the car easy for a 20 year old, no cruise control though so it gets annoying.

Ouch, that doesn't bode well for me...

My '01 T/A M6 get's around 13mpg right now...only mods are LID and Magnaflow CB. I do drive pretty aggressively, but my 94 LT1 (M6) under the same driving got 18-21mpg.

No check engine light or anything.

My 2002 3.8 litre camaro gets around 33 on the highway... I put about 430 miles on the tank with an average speed of about 105-110 and when I did math on it, it said 29.98 mpg at an average speed over 100mph...

My Z28 has gotten as much as 360 miles to a tank, before the tune up. I'm hoping a tune on the Z28 should get me around the 29mpg area, right now highway is looking to be about 26mpg A4 3.23.

and put it in Neutral going down hill.

Isn't that bad for the car? maybe I'm wrong..

I'm not sure on that one :confused:

Ok. On my next trip I'm going to try tailgating a semi to see how much it helps.

Isn't that bad for the car? maybe I'm wrong..

Actually, I think it may be illegal and bad. I know in a big truck its illegal, and if your caught doing it, its something to be pulled over for. They consider it "not being in control of your vehicle". I'm just assuming its similar in a passenger car...

Actually, I think it may be illegal and bad. I know in a big truck its illegal, and if your caught doing it, its something to be pulled over for. They consider it "not being in control of your vehicle". I'm just assuming its similar in a passenger car...

On the legality of the issue I am not sure, but it is a standard technique to hypermilers...

http://www.driverside.com/auto-library/hypermiling-195

On the legality of the issue I am not sure, but it is a standard technique to hypermilers...

http://www.driverside.com/auto-library/hypermiling-195

Coasting and Braking
Basic: Coast to a stop with as little braking as possible and go slow enough around corners that you don’t need to brake. Coast down hills by laying off the brakes and gas, and push in the clutch if you’re driving a manual.

So lets just burn up the clutch....

Hardcore: While gliding, put the car into neutral and wait until you hit a low speed of about 15 mph under the speed limit. Shifting into neutral increases fuel efficiency, but means you don’t have complete control of your vehicle, which is dangerous and illegal in some states.

Like I said, Its not legal for truckers, and some states for cars eaither since you lose "control" of your car...

Good read though thanks for the link.

I don't know how they would ever find out, unless they pulled you over for not sounding loud enough, lol.

The only time that I tried it was when I had HPTuners open logging MPG on a road trip. I was definitely avoiding the law on that trip while tailgaiting... but not tailgaiting at 5 feet, more like 25 feet.

How would you burn up the clutch in neutral (assuming your clutch fully releases)?

I don't know how they would ever find out, unless they pulled you over for not sounding loud enough, lol.

The only time that I tried it was when I had HPTuners open logging MPG on a road trip. I was definitely avoiding the law on that trip while tailgaiting... but not tailgaiting at 5 feet, more like 25 feet.

How would you burn up the clutch in neutral (assuming your clutch fully releases)?

I was refering to the statement on that hypermilling site that talked about basically riding your clutch with it all the way pressed in down a hill....its not good for a clutch...now if you put it in neutral and were not on the clutch, it wouldn't tear it up obviously but if your riding your clutch..yes it could tear it up...

I guess you can't coast with an automatic, right?

lol with the car in my sig I do 90% city driving and went 120.0 miles on 12.05 gallons last time I filled up

I guess you can't coast with an automatic, right?

It would probably be better on the tranny to coast with an auto then with a manual.... either way riding the clutch is not something you should do.

And coasting in neutral is illegal in some states and illegal for big trucks to do in all states pretty much.

lol with the car in my sig I do 90% city driving and went 120.0 miles on 12.05 gallons last time I filled up

10 mpg?? LOL OUCH...