Lousy gas mileage
Thread Starter
Heel & Toe
Joined: Jan 2008
Posts: 19
Likes: 0
Lousy gas mileage
I have a 97 C5, which use to get good gas mileage. I took the car across country and averaged 27 MPG. After returning I changed the rear end to a 3.42 and changed the torque converter to a 3200 or 3400 stall. Since these changes I have only been able to get about 17.5 MPG.
Is this a normal decline for these changes?
Thanks
Is this a normal decline for these changes?
Thanks
Safety Car
Joined: Aug 2004
Posts: 4,734
Likes: 232
From: Youngstown Ohio
I don't know if that would be considered normal or not but I bet you are having a great time with the 3.42's, big improvement in grin factor from the 2.73's, assuming thats what you had. Could your foot be in it a bit as of late, when I went to 4.10's mine was. ( I have a manual BTW )
Also, big difference going cross country to around town/freeway mix. What miles per were you getting around town normal driving before the switch. My miles per went down too but I realized I didn't really know what I was getting in normal local use, only on the freeway.
Maybe take the car on a the freeway and see what ya get, if ya haven't already and see what ya get. When I did get a chance to go on a freeway trip I found out I lost about three miles per, not so bad. What I lost around town I have no idea because I really don't know what I was getting before hand.
So, how do ya like the new gears from the fun factor? For me I will never go back.
Darion
Also, big difference going cross country to around town/freeway mix. What miles per were you getting around town normal driving before the switch. My miles per went down too but I realized I didn't really know what I was getting in normal local use, only on the freeway.
Maybe take the car on a the freeway and see what ya get, if ya haven't already and see what ya get. When I did get a chance to go on a freeway trip I found out I lost about three miles per, not so bad. What I lost around town I have no idea because I really don't know what I was getting before hand.
So, how do ya like the new gears from the fun factor? For me I will never go back.
Darion
Melting Slicks
Joined: Nov 2003
Posts: 3,011
Likes: 9
From: Dublin GA
No. that is not normal
My wife and I both have stalls and 3.42s and she averages 27+ hwy, and 21-22 daily driving city and hwy.
If it's NOT your right foot...
Check for codes. You may have a bad O2 sensor or something affecting your AFR.
My wife and I both have stalls and 3.42s and she averages 27+ hwy, and 21-22 daily driving city and hwy.
If it's NOT your right foot...
Check for codes. You may have a bad O2 sensor or something affecting your AFR.
Last edited by Blow Torch; Feb 9, 2010 at 01:49 PM.
Instructor
Joined: Jun 2009
Posts: 109
Likes: 6
From: Scottsdale AZ
Bikerman,
The changes you mentioned may have contributed to the reduced fuel economy you are experiencing. I have an 01 coupe with 35K miles and was (in my opinion) not achieving the 18/28 MPG stated by GM. I did the usual stuf like replacing the air filter with a K&N, cleaning the MAF sensor, etc. Even then, I was not near the 18/28. A fellow member here sugested I change the Two forward Oxygen sensors. After I did that, I was on target with the expected MPG. I filled the tank and entered the Freeway for 15 miles and the MPG was 30.5 MPG. around town it was approximately 18 MPG if I did not drive hard.
Thought I'd pass this along.
Sledge_78
The changes you mentioned may have contributed to the reduced fuel economy you are experiencing. I have an 01 coupe with 35K miles and was (in my opinion) not achieving the 18/28 MPG stated by GM. I did the usual stuf like replacing the air filter with a K&N, cleaning the MAF sensor, etc. Even then, I was not near the 18/28. A fellow member here sugested I change the Two forward Oxygen sensors. After I did that, I was on target with the expected MPG. I filled the tank and entered the Freeway for 15 miles and the MPG was 30.5 MPG. around town it was approximately 18 MPG if I did not drive hard.
Thought I'd pass this along.
Sledge_78
Le Mans Master
Joined: Sep 2003
Posts: 8,847
Likes: 795
From: Longview Texas
I have a 97 C5, which use to get good gas mileage. I took the car across country and averaged 27 MPG. After returning I changed the rear end to a 3.42 and changed the torque converter to a 3200 or 3400 stall. Since these changes I have only been able to get about 17.5 MPG.
Is this a normal decline for these changes?
Thanks
Is this a normal decline for these changes?
Thanks
My in-town mileage is much lower than the highway mileage. Look at the average speed on your Driver Information Center. Even with a mix of highway driving, the average speed is often down around 30 MPH.
Pro
Joined: Jun 2009
Posts: 552
Likes: 4
From: Mukilteo WA
I'm getting 13.x with 3.42's and 3200 stall.
I get a bit of a fuel smell in the garage after a cold start.
I have no codes so what are the chances my O2 sensors are bad?
Could it just be the long tubes and cam required a rich tune?
I get a bit of a fuel smell in the garage after a cold start.
I have no codes so what are the chances my O2 sensors are bad?
Could it just be the long tubes and cam required a rich tune?
