View Full Version : gas milage...

07-29-2005, 09:55 AM
Hey, all of a sudden.. (well, i dont really know when exactly, as i rarely drive my gn) my gas milage went to $hit. I mean a half tank, doesnt really get me anywhere these days. Last weekend, I had a little more than a quarter tank, drove it 10 miles, now Im on E. Theres no gas leak at all, but its been around 95 here during that time. What exactly affects the mpg in our cars, and does the ambient air temperature and/or humidity affect mpg? Tell me everything I should look for. I'll replace anything it takes, to keep my mpg up. The only things that were done to the car, performance wise, is an old kenne belle chip, a 9" cone air filter, and a stage 3 shift kit. Would turning up the fuel pressure have anything to do with that? also, if I were to dump some of that 'injector cleaner' crap into my tank, does it clean as efficiently at low throttle as it does high throttle, or does that matter. or is that stuff a total waste of time. my other question was, if my injectors were all clogged up, but i have the fuel pressure raised a couple of pounds, what sort of even things out? whats a good pressure for cool days, and a good pressure for really hot humid days. I hear you have to adjust for such conditions..

07-29-2005, 10:08 AM
The old Kenne-Bell chips are dated technology. Get something from this century. And from a good source. TurboTweak, Red Armstrong, Jay Carter, etc.

Running higher than necessary fuel pressure will just waste fuel. About 40-43 PSI should be all you need.

In tank injector cleaners are typically worthless. Chevron "Techron" (NOT "with Techron"...just straight Techron) is one exception. However, removing the injectors and having them cleaned on a RAM/ASNU injector machine is the right way to do it.

Weather affects gas mileage, period. You need to look at the car with a fuel pressure gague and scan tool to really see what is going on.

07-29-2005, 11:27 AM
Yea, I know its an old chip, but thats what came in the car. I Have a few more upgrades to do, and Ill need a chip to tie all those in together, and dont want to purchase another, and then have to take it out anyways. (unless it will be THAT much of an improvement) what exactly is soo much better about the new chips. i dont know too much about chips, and am very curious. my fuel pressure is at 40 even i think. and im taking it, that the hotter it is, the lower the mpg? I was going to clean and flow my injectors but, im gettin the 60lbs mototrons anyway so, ill just throw some of that stuff you recommended for now ;) thanx for the info.

07-29-2005, 11:50 AM
You will have to get a chip to go with the injectors, as chips have an injector constant set in them as well as tables of values set for the injectors...

08-01-2005, 12:03 PM
Well all I know is, when I hit the quarter tank mark, it's all over for me. could my gas guage sensor/sender thing be bad? again, my guage says a quarter tank, i went to the car show, (11 miles there), came home, and It's all gone. so thats 88 miles to a tank? Theres no leak on my driveway, but, theres got to be something wrong man...

08-01-2005, 12:32 PM

If you're only getting 88 miles per tank, your mileage is more like 5 MPG or less.

You have not assessed your mileage based on a tankful. (Or a series thereof to get a running average...) Just a reading based on a fraction of a tank. And the guage does not read fractions well. Could your guage be fried? Sure! Could your car be malfunctioning? Likely. Could your assessment of gas mileage be WAY off. I'm betting quite a bit.

I realize springing for a full tank (or 2...or 3) of premium requires a major investment, bordering on home loan levels these days. However, I think that is what will be required before you can get an answer to your own question.

If you're not up on calculating MPG, see http://www.edmunds.com/advice/strategies/articles/106074/article.html Your car should have a trip odometer, which helps.

Just a thought...

08-03-2005, 11:56 PM
i fill my tank. what i was sayin was rhetoric. sarcasm. everything is ok.. ive never paid attention, because i rarely drive this thing. actually, it rarely gets to the quarter mile mark as well. but i decided to let her go this time, because i wanted to throw in some injector cleaner soon. and when it got to one quarter tank, i drove 11 miles to the place, came home, 22 miles so far, and it was totally on E. if thats 22 miles per quarter tank, thats 88 miles per tank there. but again, i was being sarcastic. (thinking out loud) i never guesstimated my mpg.. it was miles per tank. again, that was frustrated sarcasm. anyways, back to the 'gauge being fried' and 'car being out of tune' part... what are some of the things besides my chip, i should pay attention to. and, if any part of my fuel guage is messed up, would that cause it to work fine, up until the quarter mile part? what would cause it to send the wrong reading.

08-04-2005, 04:30 PM
Quarter...mile? Quarter...tank? This thread is making less sense with every post... :confused:

My last comment: The TR fuel guages seem to be non-linear. That last bit sinks a lot faster than the rest. Actually, every GM car I have is that way. Perhaps just gravity working against the float.

Good luck.

08-08-2005, 04:06 PM
so it is non linear...that makes sense... thanx

08-08-2005, 11:04 PM
My experience with most GM cars up to 1991 is that the "half" from Full to a half tank is notably more than the "half" from half-tank to Empty.

That is, if I hit a half-tank after driving about 250 miles, I can expect the "low fuel" light to kick in around 360 to 390 miles or so.