Just thought I would post up a thread since gas prices are getting CRAZY now a days, and lots of people are debating on doing certin mods (like me)

What's your TBI car get for fuel mileage?

Please let us know the main things you have done like
Tire size
Rear gear ratio
Exhaust mods
Fuel pressure bump
CAI
Bigger TBI
ect......
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My car is completely stock 91 RS A/T
Stock 16" wheels
2.83 rears

26city/34-38 highway
can go about 455 miles on a tank.

 

well so far ive done

Hooker Super comp headers w/ 3" full exhaust and Flowmaster 80 series
Accel U Groove plus and yellow Accel 8mm wires
Accel Distributor Cap and Rotor
Edelbrock open element w/ K&N filter
1" Throttle Body Spacer
Catylatic Converter Delete

I was getting around 18 mpg before i cut the cat off, but now with my cat off my egr valve wont work so i maybe get 15 if that. I can fill my tank cost me 45 dollars and maybe only go 210 miles in the city... My check engine will come on when it rains of for no reason then turn off bout 5 mins later... My engine runs rich, so im going to put a new HI FLOW cat on and see if that helps with the gas mileage...

 

when it had a 305 tbi my 9 formula was at 24 city/31 highway.... if i kept my foot out of the gas.

3.42 gears
edelbrock manifold
open air cleaner
1.6 rockers
smog removed
everything else stock, and it was at 227,000 miles when the running 305 got pulled for a 426 hp 350.... now on a good day i might get 10. damn i miss that 305

 

You sure you aren't having a problem with your speedometer recording miles? I'm having a very hard time believing those numbers. Thats better than your average brand new Honda Civic.


Anyway, if I'm nice my 350 TBI gets about 16 city and 26 highway. 3.42 gears, auto trans, 193 heads, weak cam, stock TBI, 65# injectors, custom chip tune running EBL. SLP 1-3/4" headers with full 3" exhaust.

 

I am positive...... I bought the car in Dallas, TX and drove it back to Chicago and only had to fill it twice to get home.

It was averaging between 34-36 MPG on the trip home at 70mph.
I since have filled the car again, and drove it 246 miles and I'm at 3/4 tank.

My guesstimate is the 2.83 rear and OD trans??

I told the wife if this thing was AWD I'd drive it year round!!
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I hear ya.... my other 91 has a hevily built 355 and averages 3-4mpg if that, then again it's only got a 5 gallon cell in the front!

 

Third gen gas gauges are inaccurate, the only scientific method is to fill, empty, fill and then record.
The 2.73 gears with .70 overdrive a highway combination.

 

Which is EXACTLY what I did !!! Trust me, I own 5 semi tractors, i know ALL ABOUT MPG

I also verified my speedo and odo with my GPS.
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Taking this into consideration.... how else could you figure out your MPG w/o a fill/empty/refill?? It's not possiable.

 

My best so far was when I filled up today....30.17 MPG. That's a combination of highway/city driving with the A/C on most of the time.

I usually average about 26-28.

Specs:
LO3-Bone stock except for open element
Swapped in T-5 (was originally 700R4, and I haven't changed anything in the computer)
2.73 rear
Tires:
front-275/40/17
rear-285/40/17

 

Very nice.............. I almost can justify the 355 Carb Swap I was thinking about doing.

 

i just bought my car yesterday, so here goes. it has 16 inch tires, and with the t-tops off it gets around 28 mpg's on the highway. im not sure about anyother info on the car yet. but this is all stock, (except the intake, has open intake). this car is designed for gas milage, and not speed. it has a 700something-or-other transmission, and has drum back brakes. but yea, 28 mpg's sounds good to me. also thats if i behave :smile:

 

Man, you guys get insane gas milage.
I get 200-210 miles/tank doing 30/70 city/highway with my 305 TPI.

 

How can you calculate your mpg the day after you bought? Already go through a tank of gas in 1 night?

87 GTA
170,000 mile TPI 350
3 year old rebuilt/shift kitted 700R4
Relocated IAT sensor
Airfoil (on when I bought the car)
K & N filter in stock intake
2 year old Magnaflow cat & LS1 cat back
Stock GTA crosslace wheels & 245/50-16s

Around town...Best is 15.6 mpg
Odometer broken now, and I drive highway miles now, after moving, but dunno my highway miles per tank nor mpg

 

Back in 2001 when I sold my brother my 96 Trans Am M6, he drove all over the place showing it off to all of his friends. He probably went through a tank and a half in a couple of days.

 

24 mpg, that was mostly highway.
350 tbi
cam
headers
3.42 gears
700r4 slipping transmission
235/60/15 wheels
no catalytic converter
single 3inch exhaust dymomax muffler
350 computer

 

My bone stock L03 Caprice nets me about 24 on the highway @64mph.

 

I get a about 14 MPG

 

I get about 20 city, and 26 on a mellow highway cruise. Its a just-tuned LO3 with 114k, stock save for a Hypertech Stage 2 w/ 160 stat, open element, Performer TBI intake and 3" catback. I look forward to adding headers this spring, and attempting to keep my foot out of it. Oh yeah, an M5 and stock 3.08s too...

 

12 GPM. I think I need a good tune up!

 

I get about 270 to 300 miles a tank in town. When I had my laptop hooked up running the EBL I was getting 24 mpg in town.

 

hard to tell what gas milege im getting when i cant keep my foot out of it lol, no im not sure on the city streets, but highway with my 700 r4, i get about 30, it does good for me, cause i used to have an 81 chevy pickup with a 350 wieand high rise, holley 650, and i didnt get ****, but that was on a th350..

 

edlebrock performer TBI intake manifold
borg warner t-5
flowmaster exaust
front tires-255/45/17
rear tires- 275/45/17

im getting about 10mpg for the city, maybe 12-13 on the freeway...i get about 150miles to the tank

 

u guys are making me cry. my little lg4 engine with 3/4 racing cams gets me 15mpg city/24 mpg highway and im not pushing out mad power either. but my engine has got blowby and the transmission is grinding. but im in the process of fixing that. i hop it works.

 

My 91 caprice had an l05, 3.08 gears, 235/60-15's got 24 mpg. Lowered it because of what that did for my brothers acura, and was rewarded with 27 mpg. also picked up 15 mph top speed.


i hop so too!

 

I'm lucky to get 14mpg.

 

the window sticker on my 89 firebird TBI 305 is 17 city, 26 highway and thats about what i get. so please tell me what the hell you have done to get 26 and 34 38 you had to have swapped a B18 in there or somethin

 

Yeah,really. Post up.

 

 

2.5 iron duke maybe?

 

Re-read the 1st post he has 2:83 gears......

The best ever (one time) mine has done was 34mpg 100% highway @65 in Lean cruse mode on a 850 mile trip in the summer at 85-90deg. I got 681 miles on 20 gallons. I can say it was probally the gas (better than normal). I haven't had the chance to try that agian. I have got 28-30 many times in the summer on trips.

 

Yea, because the steeper the rear gear the better your mpg, that makes tons of sense. These site is steadily digressing...

 

yep with 2.83 in the rear and my old tb 305 i got 29-31 on highway and 16-18 in city

my civic get 24 in city n 28 on hway--with 228500 miles no rebuild and qt of oil every 300 miles--and i'm the only owner

 

It looks like I have to do some math to find my most efficient RPM. I'm close at 70 in OD with my 2.73 rear. Maybe I should try a vacuum guage.

 

Last time I checked, I got about 22-23 mpg combined. That's with the 16x8s, auto, 3.23s, open element breather (behind the functional SS hood) and the Jett II chip (boo, I know). I use the skinney pedal too much, though. I'm gonna fill up tomorrow and see what I get.

 

455 MILES /15 gallons = 30.33 MPG.

Record what you put in when you fill the tank...only way to measure.

My old bone stock (ok some Trans work) got 30mpg (auto/2.73)

and everyoneelse saying 2.83---they are 2.73s!!!

 

I have an all stock 89 RS (LO3 & 700R4). City mileage is about 23 mpg and highway is about 31 mpg.

 

1989 RS Camaro in sig.
305, shortie headers were on it when I bought it. I added a full exhaust which helped alot. 3 inch high flow cat, and a flowmaster. Pretty sure tires are stock front, and about an inch wider in the rear.
5 speed, 3.08's, G80.
Running rich I got 22 or 23. Going 80. Don't remeber anymore. Never checked it after I fixed it either.
Speedo dosen't work so I had to use my GPS, which is more accurate anyway.

 

WHAT THE HELL DO I HAVE TO DO TO GET THOSE NUMBERS? I AVERAGE 18ISH ABOUT 60/40 HIGHWAY/CITY 3.08 GEARS. OR MAYBE I AM GETTING THOSE NUMBERS? LAST TIME I FILLED UP IT WAS 15 AND I WASNT IN IT TOO MUCH BUT I DID HAVE FUN WITH IT ON THAT TANK.

AND SOMONE SAID PUTTING CAT ON BETTER MILEAGE?


ALSO, I KNOW THAT NEW O2 SENSORS WILL HELP BUT I DONT KNOW IF MINE NEED REPLACED? MY CHECK ENGINE LIGHT NEVER COMES ON. SO I THINK ITS NOT WORKING. IF IT DID I COULD PROB FIX ALOT OF PROBLEMS WITH HER

 

I get about 22mpg. Its a 1989, auto, 2.77 with factory 15s.

 

its a 10 bolt right? They are 2.73s with a 10 bolt---2.77 was a 9 bolt ratio

 

Just take your car to Advance. They should have a tool that'll hook into the ALDL port and make your light flash and you can see what codes it shows. But, if the light is dead, you won't know. Might try replacing the light.

 

No need. Autozone keeps giving me those keys and you can accomplish the same thing with just a paper clip.....

ECM codes

 

No I have a 9bolt with disk brakes. I have 2.77 not 2.73.

 

stock lo3 with open element
700r4 with 2400 tci stall
stage 2 transgo with corvette servos
3.73 torsen posi

somewher between 15-18

 

1989 Camaro RS
350 TBI
5 spd
Holley TBI
Personally tuned chip
Everything else is stock

Just driving around town i get about 19mpg, i attribute that to my chip tuning, i dont think 19 is bad for a 350 around town, heck i only get 15-16 in my F150 with a 4.6L in it around town.

 

91 RS, 305 TBI, WC T5

255/40/17 front
285/40/18 rear

Open K&N with X-Stream lid, SS hood
Hooker shorties, 2.50in duals, X-Pipe crossover, Flomaster single chambers
Ultimate TBI mods part 1
Whatever the stock open rear is...


Best was around 28mpg on the interstate, town not so sure. Love the sound of those pipes too much.

Max,

 

Stock would have been a 3.08 peg leg, with a 305TBI/T5.