im just wondering whats the most gas anyone has ever been able to put in a 3rd gen. i have a 1989 firebird formula, and the most gas i've ever been able to put in it is i think around 13.5 gallons, and that was like chugging to the gas station b/c i was so low on gas. please let me know. also wahts the most anyone has gotten to a tank??? i think my best is 150 miles to a tank!

 

Standard capacity is 15.5gal for the tanks, but I believe certain cars (1LE's?) held upwards of almost 18gal.

150 miles out of a tank is horrible. Are you always laying into the throttle all the way? I have no idea what kind of gas mileage I'm getting with the 350 so far because I don't have a speedometer at all (need new VSS unit). I'm sure its not good though. My car isn't tuned at all for this cam/intake/heads.

On my old TPI 305, I was getting between 16 and 21mpg around town with auto and 2.73s. When driving hard, it would be around 14-16mpg depending on "conditions" When I drove to the dunes and back the day after prom, I got averaged something like 28mpg on the highway. Not bad for hitting 120 or so a few times on the way there to scare a particular passenger. On the way home, I had a few different passengers (3 girls, averaging probably 110lbs each) and we coasted at 75ish the entire way home. Only hit the brakes once to drop to 50 for a short time.

 

lol well, the way my car is running right now is amazing, compared to how it has run in the past. when i had the 305, i was lucky to get 100 miles to a tank. my motor is brand new, and so is everything else, i really dont know why my milage could be so bad, the only thing i could think of is tuning, but i had a custom chip burnt for my setup recently, and the car runs fine, plugs look nice and brown...... i dont beat on it a lot at all.

 

Well, I put in about 16 gallons once...

GM had an update program on the gas tank in my car. All I can say is that they must have somehow changed the fuel sender relationship to the tank because when the needle touches E, you better be at the pump...

No big deal now since I know it, but was not happy at the time!!

BTW - about 25 mpg on the highway. I don't bother checking in town.

Engine internals are stock.

Have basic bolt-on's, UD crank pulley, Accel Supercoil, K&N's, SLP chip, and SLP cat-back.

 

i have an 86 t/a with tpi 305. the most i hav ever been able to put in it is 13 gallons. i only get about 120 to 130 mpgs. something is wrong with my car. i know is should be getting better milage than this.

 

i have an 86 t/a with tpi 305. the most i hav ever been able to put in it is 13 gallons. i only get about 120 to 130 mpgs. something is wrong with my car. i know is should be getting better milage than this.

 

finally someone like me that doesnt get like 200 billiion miles to a tank haha maybe we have the same problem

 

I have gotten 24mpg driving highway. 5th gear just cruising along at 70 with the cruise on.

After that, anything in the city is horrible.... I would guess somewhere around 14-16 with my stock TPI 305

Most I have put in was a little over 13, but I was a lil afraid to test it

 

well thank ***, i guess my milage is somewhat normal thanks guys

 

I average 16 mpg intown and 23-24 on the highway. I kinda race it around alot though. Most I put in there was 11.5 gallons

 

somehow my car stopped at 6 gallons after the gauge was on E...im lost there lol. Either something is wrong with the gauge and i had a full tank, or i really only have a little under half a tank of gas.

 

i would kill for 16 mpg in the city. i get something like 9-10. i think some of my fuel injectors are messed up. i'm going to check them today.

 

yah man, definetly get those checked for leakage, that would kill your milage

 

i had 5 injectors with cracked tips. replaced them today

 

LOL well that would do it, let me know how the car is!

 

lol, i clicked on this thinking it was about nitrous

 

Something must be wrong with either my car or your guys cars because I just took a 268 miile drive and it was 10.6 gallons between fill-ups. This was a comibination of mostly highway, some freeway, and some city sidestreet driving.

I would not say I drive the car hard, but if I need to pass I don't drag it out and if I need to set up for a lane opening, etc, I don't hesitate to use the go pedal....

Just put in new Bosch/Ford injectors (22#), but but before a couple of the OEM Multecs went bad, mileage was about the same.

 

i average a little over 14 gal. each fillup. and i get about 18 miles to the gallon city driving out of my 350. my friends 88 transam with a 305 tpi never fills up more than 13.5 gal. amd he gets 15 miles to the gallon..i think. we have noticed the differnce before when we were both filling up. we cant figure it out.

 

yeahh, i guess that makes sense.... maybe im missing something, there is a small crack in my neck of my tank, b/c when i did the pump i had to bend the neck a little, and i cracked it where it meets the tank in a small spot, so now my tank wont seal, but i dont think that would have anything to do with milage.... i mean gas cant evaporate THAT quick can it??? maybe its just evaporating, and thats why im getting bad milage??????? but the crack is reallyyyyyy small! i dont hear the tank being depressurized ever anymore though.

 

I can usually put 50 litres into the tank, 53 litres was the absolute most i've crammed into the tank before. (55.x is the 15.5gallon mark)

On average with a 350 auto with 3.27 gears, lots of playing around too, I get 230-250 miles. 313 miles out of a single tank of 104 octane was the best i've ever gotten outta the car. Don't ask me how, but for whatever reason it ran like a dream on that race fuel.

 

150 kilometers is only 1/4 tank for me...little more... im guessing i get over 400 km to a tank, not sure how many miles that is.

and i only have 700r4 with 410 gears.

 

LOL any input on my last post?

 

Just want to clarify my previous post. That was 268 miles on 10.6 gallons of gas for just over 25 MPG...

Gas does evaporate very quickly, but not sure the average rate or if it would be the culprit.

Certainly there should not be nearly a 40% (or so) mileage difference in cars that are similar unless driving styles are WAY different.

 

i definetly do not beat on my car a lot..... im so confused, i have brand new everything ahhhhhh

 

Maybe you arent getting proper fuel pressure because of the crack in teh filler neck?

Im not sure, but you shouldnt be getting that bad of mileage...

Have u checked to see if your car is running rich or if youve' put larger fuel injectors on you will be using more fuel thats for sure.

 

yeah, i know, i think maybe its just in the tune. we'll see about that...

 

My mothers 89 350 IROC all stock with 2.77 had gotten 340mi with 1/4 tank of gas left on the open highway. My car has gone about 270mi with 3.45 gears.

 

LOL dude thats absurd, i cant believe that, im sorry. and merc, i dont think thats possible b/c the pump is submerged, so i dont see how that would effect the pressure, you know?

 

Ah ok, not 100% sure then how the tank pressurization works. I thought that the pump actually pressurized the tank to help with forcing gas into the system and didnt rely on gravity/pump mechanics to do all the work.

Thats why I figured with the crack in the filler neck (since it should be a sealed system with the gas cap on tight) it wasn't holding the pressure.

 

you said you put a chip in it. is it one that requires a low restriction exhuast and a 160 thermo? if you have one like that and didnt put a 160 thermo in thatll wreck your cat and ur o2 sensor which leads to poor gas mileage but not as bad as yours is getting.

 

lol well my chip was burnt exactly for my setup. so i dont see how it would effect anything :-/

 

well then its definitely not any of the stuff i said then.... good luck finding out!

 

thanks lot guys, i appreciate all the help

 

just bought my 87 ta 305tpi. it sat for over a year before we picked it up. we went and got it,drove it to a gas station put in 1/2 tank of cheapy gas (the first half is over a year old) then we drove it 180 miles home continued to drive it all over town. I finally put gas in at around 250 miles and it took 12 gallons.
We put $100 of tune up parts and a brake shoe on and she is getting better milage than our trip(even pssed new york inspection with out a flaw).
Not bad for a fast fun TA with no rust,dents or issues. OH to top it all off I bought it as a parts car for $661. Gotta love EBAY
It gets such great gas milage I gave away my 4cyl olds. Who needs a daily driver when your trans am gets over 20mpg

 

do yo guys think theres a noticeable difference in gas milage between the 5.0 and 5.7 liter engines?????

 

A stock 350 car should average about 20 miles to the gallon with mostly town and some highway driving

Both my 91's did that easily being 350 cars.

Should pull 22-25 on the highway on a regular basis as well.

One tank wonder doesnt count as consisitent mpg either. My results come from keeping track using the trip odometer and always tracking mileage on trips. Jamming the tank to the brim on one stop makes your mileage worse, just as stoping when it first clicks at the pump makes it better. (unless u always stop at first click or always jam in most humanly possible)

My current 383 avg just shy of 22mpg on the highway. Hovers in the 18-20 range around town driving.

My old hotcammed vortec headed 350 was capable of about 23mpg on the highway and also avg'ed about 20mpg with mixed city/high driving when driving to my old job.

If your getting 15mpg or even 18mpg(unless only around town cold starts) you have something wrong with your car and should really look into it. Or it could be you drive like a fool and stomp it from every lite. It will only save u monye in the long run, especially with gas price raping we have currently.

later
Jeremy

 

I get about 18 mpg, but I tend to play a lot. As for how much gas I've put in there. The first time I filled it I put 22 gallons in it. Only to find out that I had a bad filler neck.

Prices SUCK (big surprise)

 

LOL whattttt so you basically poured out like 7 gallons of gas???

 

My 89 firebird XS with 2.8 liter automatic gets about 21-25 miles per gallon. City and highway driving.

I normally get down to a quarter of a tank so around 12 gallons. Then fill it up.

This is my daily driver 44 miles a day round trip to work and back.

Gas prices are crazy. 2.87 a gallon for regular unleaded.


Bruce

 

I got about 18 around town on a totally stock setup. Don't drive it on the highway very much so I can't say.

I could understand same or sorse mileage in a 305 since it has to "work harder" than a 350. Look at the minor differences in a newer V6 and an LS1 and you'll understand.