Why did I lose some MPG
Thread Starter
Burning Brakes
Joined: Aug 2002
Posts: 862
Likes: 41
From: Mahwah NJ
Why did I lose some MPG
I have an 02 Zo6 with Vararam, Kooks longtube headers, computer tune, K&N filter with 31k miles. I used to get 30.4 mpg on the highway In 6th gear at 75 mph. Now I'm only getting 26-27 mpg with the same setup and can't figure out why. The only thing I changed in the last year was the K&N filter and oil. Tire pressure is perfect on my Pilot Sport ps2's and i put a bottle of Techtron fuel system cleaner in the tank every few months of driving.
Can anyone provide some Input on what I should check???
Can anyone provide some Input on what I should check???
Safety Car
Joined: Jun 2004
Posts: 4,986
Likes: 393
From: Stoney Creek Ontario
A few yrs ago mine acted up the same way - lost mpg, only thing I could figure was to change my plugs/wires, which picked it right back up again......yours' dosn't have a lot of miles, are the plugs and wires original? They're 10 yrs old of they are...time takes it's toll as well as mileage.....sometimes bad 02 sensors can do it a well, but you'll likely see it in the exhaust smoke and smell the richness...
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
I have an 02 Zo6 with Vararam, Kooks longtube headers, computer tune, K&N filter with 31k miles. I used to get 30.4 mpg on the highway In 6th gear at 75 mph. Now I'm only getting 26-27 mpg with the same setup and can't figure out why. The only thing I changed in the last year was the K&N filter and oil. Tire pressure is perfect on my Pilot Sport ps2's and i put a bottle of Techtron fuel system cleaner in the tank every few months of driving.
Can anyone provide some Input on what I should check???
Can anyone provide some Input on what I should check???
And ethanol is junk
Team Owner
Joined: Jan 2007
Posts: 29,063
Likes: 1,839
From: cookeville tennessee
I have an 02 Zo6 with Vararam, Kooks longtube headers, computer tune, K&N filter with 31k miles. I used to get 30.4 mpg on the highway In 6th gear at 75 mph. Now I'm only getting 26-27 mpg with the same setup and can't figure out why. The only thing I changed in the last year was the K&N filter and oil. Tire pressure is perfect on my Pilot Sport ps2's and i put a bottle of Techtron fuel system cleaner in the tank every few months of driving.
Can anyone provide some Input on what I should check???
Can anyone provide some Input on what I should check???
with the guys above but also can be in the tune that you went with in the car....
Robert
Last edited by robert miller; Oct 14, 2012 at 12:21 PM.
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Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
My guess would be plugs, wires, dirty MAF or slowly failing O2 sensor.
I just can't see an air filter having much effect on the fuel mileage of these cars.
http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf
Jump to page 37 to see the conclusions.
A similar thing would apply to the fuel filter. Either the fuel gets through enough for it to run or it doesn't.
I just can't see an air filter having much effect on the fuel mileage of these cars.
http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf
Jump to page 37 to see the conclusions.
A similar thing would apply to the fuel filter. Either the fuel gets through enough for it to run or it doesn't.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Clean you MAF and TB and make sure that your not getting any un metered air in the intake system.
You need to data log after that to see where your Long Term Fuel Trims (LTFTs) are setting. They SHOULD be close to zero. If you were getting that good of fuel mileage before they were. Where are they at now???
If they are HIGH,, thats the issue. Winter fuel contains more ethanol so the efficiency will also go down.
BC
You need to data log after that to see where your Long Term Fuel Trims (LTFTs) are setting. They SHOULD be close to zero. If you were getting that good of fuel mileage before they were. Where are they at now???
If they are HIGH,, thats the issue. Winter fuel contains more ethanol so the efficiency will also go down.
BC
Melting Slicks
Joined: May 2008
Posts: 2,606
Likes: 355
From: Rochester New York
Going to have to agree with Ethanol. If you changed where you fuel your car, or if the fuel near you has changed to E10, you will see 1% to 3% decrease in fuel efficiency going from gasoline to E10.
Also, check with your tuner, you should be running a stoich AFR that matches what fuel you are running. A lot of tuners are still running cars at 14.7:1 AFR when they should be more like 14.1:1 with E10.
Also, check with your tuner, you should be running a stoich AFR that matches what fuel you are running. A lot of tuners are still running cars at 14.7:1 AFR when they should be more like 14.1:1 with E10.