jay97lt1

I have a 98 Trans Am A4 3:42 gears all stock with ORY and corsa exhaust.I want better MPG's I drive 94 miles a day for work and it gets around 20 MPG.

KevinR

I would just buy a little beater with a 4 banger in it if I were traveling that far. You MPG is pretty low for it being what it is..

metalmilitia606

iTrader: (8)

I have to agree with the above post. With an auto you're not going to see much better MPG's than that. My old auto Z28 got about that much. Remember these cars weren't built for MPG's they were built for SPG's (smiles per gallon) lol.

TheBlueKnight

iTrader: (4)

Best answer you will get is people telling you to do your maintenence. Spark plugs, fuel filter, air filter...ect... Only thing I could think is if you go get a tune and they lean you out a bit. The factory tune is fairly rich.

thunderstruck507

iTrader: (18)

if your car is well maintained and you're granny driving and you're still not happy, buy a beater for under $1000

there is no magic trick to pour in your tank or stuff in your intake path that will give you better mpg

1) keep the car well maintained (including tire pressure)
2) try to avoid ethanol added fuels
3) drive like there's an egg under the throttle
4) avoid idling
5) drive the speed limit or lower

GIVE EM' THE BIRD

iTrader: (1)

Throw out those 3.42's. Lid and exhaust. Maintain it well, and drive slow.

01 ss vert

iTrader: (1)

O2 sensors if they are old might make a difference.

thunderstruck507

iTrader: (18)

3.42s shouldn't be hurting much if at all....my highway mileage actually seemed to get better from 3.08 to 3.42 because the engine wasn't lugging when staying under 80mph

tmdz28

iTrader: (2)

Cant expect a car with 300rwhp to get 30+mpg. The saying, cant have your cake and eat it too comes to mind.

Solution: Get two cakes, one to eat, one to have!

I DD my 2003 corolla with 150k miles that gets consistent 32+mpg. On the weekend, that's when i dont give two ***** about MPG.

jay97lt1

it would get 26-28 @70 with 2:73 gears Just installed a 40k junk yard motor 02"s are new seems like gas milage droped after motor install.

RPM WS6

iTrader: (3)

My 2.73 A4 LS1 gets noticeably better expressway MPG than my 3.23 A4 LS1 did. Only a couple MPG, but it is noticeable. With a 2.73 to 3.42 swap, and him driving at the same expressway speed, I would certainly expect a loss of MPG.

A stock engine can cruise along at a very low rpm without surge/lug/buck. A modified engine will obviously be a different story.

Sounds like majority of the OPs problem happened after an engine change. What else was changed with the engine? Injectors?....maybe they need to be cleaned. I would suggest cleaning the MAF as well.

If maintenance is up to date, tuning is correct for your engine/setup, tire pressure is correct, you're not carrying tons of extra weight, you have no DTCs, and you have no other driveability issues, then there is nothing else obvious to check. You could do a compression test, then depending on results a leakdown test, could also Seafoam the engine.

bayer-z28

iTrader: (14)

Get it tuned and keep you foot out of it.. a LOT of MPG is driving habit. My H/C LS1 gets 28mpg highway and about 13 city. Don't use the gas if you don't need it, take your foot off earlier and try and avoid hard starts. Give it about 20% throttle and let the vehicle catch up to that before you give it more. TLC does a LOT for this too.. and Seafoam, Seafoam, Seafoam, Seafoam... Tank, oil and down the throat every couple months till it's cleared out pretty well.

Sometimes gears will help city mpg. My "sweet spot" is keeping it at about 1900rpm on the HW, but that's a cam, too.

$750 L98

iTrader: (7)

I have 2.73s, a lid, headers, and exhaust. It runs about 12.4 AFR and pulled down 30mpg from Houston to Austin. I average probably 23-26 on a tank between highway/city. These things aren't that bad on gas!

Now try driving a cammed, stalled, geared 6.0 everyday.

Like others say, one to eat, and one to have! My 1989 is the toy, and the 1999 is the DD!

tmdz28

iTrader: (2)

Damn, i have never driven full tank of freeway, but with LA traffic and more green/red light than a candy store, i average between 18 - 20mpg. And that's a 6 speed. Replaced plugs, wires, fuel filter and both top o2 sensors, and recently got it tuned to peg the AFR at 12.6 at WOT.

I think these cars do get excellent mpg on the freeway, in the city, not so much.

$750 L98

iTrader: (7)

That is most certainly the killer for gas mileage. In my GF's cobalt (which naturally I drive like a d*ck) I can get the mileage down to about 22mpg in the city lol!

Starz T/A 17

iTrader: (6)

A Lid should help a little, but the only real thing you can do is get new gears in the car. I had a A4 with 342's and got right around 21-22 straight highway. Before the gears nothing else really changed the exact same car got 26-28 MPG straight highway with 273's. They will make a difference, and if you drive enough will eventually pay for themself. And 273s were an option for these cars so its not like it will be completely gutless just not as much pep as the 342s.

jay97lt1

I changed the motor myself plugs,wires,o2s are new.wiring harness and injectors came off my old motor.I have not seafoamed the motor yet.Car has a 2500 stall in it.My 97 383M6 4:30 geared Z28 gets 17 mpg so I just thought my Ta should be getting alot better

NC98Z

iTrader: (1)

Use your cruise control and just because everone else is running 80 mph in a 60 doesn't mean you have too!

Starz T/A 17

iTrader: (6)

Generally the 6 speeds get better MPG's and gears have less of a effect on their MPG's because of how low 6th gear is geared.

Kevin01Z28

iTrader: (8)

I recently put bosch o2's on my car and noticed my fuel trims were rich, particularly at idle where they were pig rich. I took them back, got denso's and my trims are normal. I didn't run them long enough to compare mileage but Im sure I would have suffered some mileage drop since the motor ran richer.