Hey: Is it the Shell Gas or the Pressure?

[Gut Check]

Gotta 04 GT Cruiser

Been lurking for over a year, and I really respect the attitude in
here. So, I don't want to incite any flames.

But I improved the MPG in my GT with a LOWERING of the tire pressures
in the 205/50-17 to 34 psi. I also get at least 1-3 MPG on the Shell
gas from this one particular station (the other in my town does not
correlate).

Anything to this, or is it just my new medications?

Also, the brakes vibrate like a kid without his Ritalin. I've had the front rotors "resurfaced" two times, but still my foot (and sometimes the steering wheel) senses the constant vibrations

[Mr.2U]

can't imagine how softer tires could improve mpg.
i run 35psi in all my stuff, seems to be a good
compromise between mpg and ride softness..


what if the one shell station has it's pumps
out of calibration, and you only think you
are putting in less gas than you are.

[SteelBlueGT]

I am running 42 psi fronts and 38 psi rears with my 215 50 17 Yoko Avid's and the ride is so smooth and nice I dont mind the high pressures. However I did not get better mpg with the taller tires. Got a slight gain in mpg when I had my computer reflashed as my check engine light would not go off and the dealer said there was a TSB that covered it.

[purple people eater]

My first thought was out of calibration as mentioned above.
But my old physics classes must have departed my memory-I can not imagine how under inflated tires could improve mpg. Just curious how that could be. Anyone?

[quicksilverdon]

Agree with other comments. You don't have your location, but is it hot and have you changed time of day when you get gas? If you get gas in very early morning, chances are it'll be denser than in late afternoon - yeah, I know tank's underground, but it will warm up. Lower tire pressure cannot help mileage.
As to your brakes - buy new rotors and stop going to wherever you're going - the rotors are too thin to be resurfaced multiple times - go to NAPA and get the more expensive rotors - they're better steel. Personally, I don't believe in resurfacing - warping occurs because the rotors don't get rid of the heat and warp - resurfacing takes metal away, so you're more likely to overheat,....

[Red GT]

I really can't imagine anyone buying a GT Turbo and worrying about MPG. I keep the tire presssure at 38 psi. as it says in the door jam for our tires. And being low profile tires, having less air between you and the road doesn't sound like a good idea. Lower psi is never good for MPG. And now summer is upon us low pressure is a really bad idea. I don't know where you are but, summer is summer. I'd keep the pressure where it's supposed to be. Low tire pressure is one of the biggest causes of blowouts in summertime. Sorry to hear about your brakes though. Mine have 29,500 on them and no problems at all.

[Gut Check]

Ok, put the pressure back to door jamb levels. Recalculated old and new data. Looks like I may have made an error in the numbers. Getting same mpg for both pressures. So forget it, the lower pressures have no effect after all.

The brakes are still crappy though.

The gas from that one Shell station is better MPG than others (maybe the pump calibration is off, but by how far, really?).

And...........higher than recommended pressures, that isn't cause for possible blowout (e.g. keeping the tire edge in the rim flang)? Yea, it is.

[JoePro]

quote:Originally posted by Gut Check

Ok, put the pressure back to door jamb levels. Recalculated old and new data. Looks like I may have made an error in the numbers. Getting same mpg for both pressures. So forget it, the lower pressures have no effect after all.

The brakes are still crappy though.

The gas from that one Shell station is better MPG than others (maybe the pump calibration is off, but by how far, really?).

And...........higher than recommended pressures, that isn't cause for possible blowout (e.g. keeping the tire edge in the rim flang)? Yea, it is.

No.
Increasing air pressure by that small margin will NOT cause a blow-out. In fact, when we doi high speed track trials, we run overinflated to reduce hfootprint by as much as 3 to 4%, and therefore reduce heat.

Underinflation causes tremendous damage to tread, belts, footprint, you name it. Increased stress on all the unsprung gear, ball jounts, etc., etc.

Joe