whats peoples average mpg on 3.4 setup?

**BlackSun** · 02-22-2011

My modded 99 knocks down 24-25 mixed, cruising at 70 it will get up around 28-30.

**Spartanzz** · 02-23-2011

yeah iv got some PB blaster so ill have to give that a try over the next few days once i get through the other problem im having.

**footballplaya3k** · 02-23-2011

Originally Posted by Spartanzz

Well this sucks...I just reached half a tank on my gas gauge and have only gone 100 some odd miles...idk what to trust the dic with how much fuel iv used or the tm gas gauge that ppl say are usually off lol any suggestion?

That's what I get. Usually ends up being 150 miles at 1/4 tank which is when I fill up.

**Silver Bullet 2004 GTP** · 02-25-2011

I think it's your tune I have the same mods on mine and I got a programed PCM at first from 3800 performance and my gas milage was 14 mpg on the highway then I got a good custom tune and now i get 28 mpg on ther highway

**footballplaya3k** · 02-26-2011

I cannot imagine how rich your car was running if you got 14mpg on the highway.

**2002gtx** · 02-26-2011

i got 23.4 mpg on my way back from NJ yesterday

**Silver Bullet 2004 GTP** · 02-27-2011

Originally Posted by footballplaya3k

I cannot imagine how rich your car was running if you got 14mpg on the highway.

It was bad you could watch the gas gauge drop

**Fierogtfreak** · 02-27-2011

I just replaced my plugs and wires and still bad mileage. How likely is it that my cat is clogged? After all my car does have 133k on it. Hopefully ill soon be able to afford headers and eliminate it but untill then i dont want it to be hurting anything.

**9ordohz** · 02-28-2011

Originally Posted by That Canadian Guy

18 for a 97 and 17.5 after that

Love that PIC (:

well anywayz..
my DIC is also accurate..

I also reset it & the odometer everytime i fill up (:

pretty accurate IMO (:

**SJAndrew** · 03-01-2011

Semi related question...

My 98 GTP is supposed to have an 18 gallon tank. I've never been able to get >14 gallons in it - when the needle is below E.

Is this normal? Upon filling it always shows full (slightly past).

Some interesting reading here. I've read similar info before (that GM has a built in fudge factor).

Basically - my question is: when I'm on E do I really have ~4 gallons "to spare"?

**addzradd** · 03-02-2011

Yes, actually for me when the needle is below E and the car is dinging at you really loud that means I have about 5 gallons and 125 miles left before I worry about filling up.

**blueguy** · 03-02-2011

You know running your car below a 1/4 tank anyways is bad for the fuel pump...right? Plus you get the pleasure of picking up all the junk in the bottom of the gas tank.

**addzradd** · 03-02-2011

Can't be that bad, my car is closing in on 200k and is still on the stock pump. Plus how much junk can be in the bottom of your tank anyways?

**TheOtherNick** · 03-02-2011

A lot, I have been surprised at the amount of crap in some tanks.

**codyAK** · 03-02-2011

Originally Posted by addzradd

Can't be that bad, my car is closing in on 200k and is still on the stock pump. Plus how much junk can be in the bottom of your tank anyways?

At 25mpg for 200k miles? 8000 gallons of fuel worth.

**addzradd** · 03-02-2011

Hey if that doesen't kill it, like I would think running it OUT OF GAS would, than idk, but it allows me to go from 6 days to 8-9 days inbetween fill ups.

**blueguy** · 03-02-2011

Because under a 1/4 tank gas sloshes around even more and picks up more bullsh1t deposits you wouldn't want going into your motor...just sayin'

**addzradd** · 03-02-2011

Idk that's what a fuel filter is for.

**SJAndrew** · 03-02-2011

Doesn't the fuel for the pump act as a coolant too? If it does run dry, even briefly, I think they can burn out.

I'm glad to know I'm not the only one who shows E when only using 13-14 gallons.

**blueguy** · 03-03-2011

Right...running low on gas also puts unneeded strain on the pump since it has to work harder to suck up gas...like a hooker tryin to find your small junk