Thread: BAD gas mileage

ive noticed this lately ive been getn bad gas mileage...
would a lower deg. than factory thermostat cause the car to run "rich" until it gets up to operating temp..???

car doesnt seem to be running bad tho...

on highway, going about 65-70mph, it stays just shy of 3k rpms..... until it gets warmer the rpms wont drop down.

Originally Posted by codyAK

I think you have no fourth gear. Switch using your shifter into third on the highway and see if the rpm's change.

??? how do you figure that..?? after driving for 10-20 min its fine.. doin 70mph at lil over 2k rpms...........

Originally Posted by bluegtp91

Did you put a lower temp t-stat in it?

It sure won't HELP your MPG's unless your tuned.

yes there is a a lower temp t-stat... 160* i think. car is bone stock
i did cause i was doin alot of intown driving in the summers...

that t-stat was put in yrs ago also... had pretty good gas mileage in the past. car has 124K ish miles on it

Originally Posted by SDGTP99

Or maybe u have a bad MAF & or TPS. That'll cause your RPMs to run high like that. Or could be a vacuum leak...

after the car gets up to operating temp, the rpms back down...
notice it more when its cold outside...

Thankx guys for posting!

Originally Posted by SDGTP99

My car has the exact same problem. Check for vacuum leaks. I didnt think I had any leaks then I pulled off my supercharger and found a leak at the boost bypass solenoid. Have your car snanned as well.

mine is only a GT, not a GTP.

there is a whooshing sound a second or 2 after you shut the car off....???
thats been there for A LONG time

Originally Posted by tc300

yes there is a a lower temp t-stat... 160* i think. car is bone stock

I would get a stock 195° thermostat in there. You're causing the engine to run at a temperature that it was not tuned to run at therefore, it is not running at it's preferred settings and taking in more gas.

Nothing wrong with getting up to temp either. 160° is pretty low also..

Originally Posted by nawarkk

I would get a stock 195° thermostat in there. You're causing the engine to run at a temperature that it was not tuned to run at therefore, it is not running at it's preferred settings and taking in more gas.

Nothing wrong with getting up to temp either. 160° is pretty low also..

thats what i was thinkn.... i put a low t-stat in there yrs ago. was doin ALOT of summer driving and the temp gauge was getn well over 220 at times. figured a 160* would keep the motor cooler and prolong the life..
had good/great gas mileage up until last summer and this past winter..??
could be time for a tune up also..