Gas Mileage
Thread Starter
5th Gear
Joined: Jun 2015
Posts: 5
Likes: 0
Gas Mileage
I have a 99 Vette which according to the on board computer module calculates MPG at 17, however in reality it is about 10-12, which I calculated by dividing the mileage traveled by the amount of gas needed to fill the tank.
Any suggestions as to why the difference?I asked my mechanic if gas could be leaking while driving and was told no. What else could cause this difference?
Thanks
Any suggestions as to why the difference?I asked my mechanic if gas could be leaking while driving and was told no. What else could cause this difference?
Thanks
Trucker
Joined: Aug 2013
Posts: 134
Likes: 10
From: Oklahoma City OK
I dunno but my MPG dropped significantly when I added headers, a vararam and 3.73 gears to my A4. The tires don't last near as long either. I can't figure it out but I can't wipe the grin off my face!
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Getting an MPG by using a manual calculation method will almost always vary somewhat from the car's computer simply because it is very difficult to ensure you put exactly the same amount of fuel back in the tank that your car burned out. But is should not vary that much.
Many say that the on board computer calculates high, but IMO it is really pretty accurate, at least mine calculates out pretty close to what I can determine using a manual method.
How is your car running - any performance issues? Have you been stuck in traffic a lot where the MPG could decrease significantly? Have you been driving differently than you normally do - i.e., more spirited driving?
Many say that the on board computer calculates high, but IMO it is really pretty accurate, at least mine calculates out pretty close to what I can determine using a manual method.
How is your car running - any performance issues? Have you been stuck in traffic a lot where the MPG could decrease significantly? Have you been driving differently than you normally do - i.e., more spirited driving?
Le Mans Master
Joined: Sep 2014
Posts: 5,278
Likes: 539
From: Kelowna BC
Getting an MPG by using a manual calculation method will almost always vary somewhat from the car's computer simply because it is very difficult to ensure you put exactly the same amount of fuel back in the tank that your car burned out. But is should not vary that much.
Many say that the on board computer calculates high, but IMO it is really pretty accurate, at least mine calculates out pretty close to what I can determine using a manual method.
How is your car running - any performance issues? Have you been stuck in traffic a lot where the MPG could decrease significantly? Have you been driving differently than you normally do - i.e., more spirited driving?
Many say that the on board computer calculates high, but IMO it is really pretty accurate, at least mine calculates out pretty close to what I can determine using a manual method.
How is your car running - any performance issues? Have you been stuck in traffic a lot where the MPG could decrease significantly? Have you been driving differently than you normally do - i.e., more spirited driving?
P.S. computer tells me 15.7 city driving.
Last edited by grantv; Nov 22, 2015 at 08:30 PM.
Instructor
Joined: Jun 2013
Posts: 174
Likes: 10
From: Wilmington DE
mileage
My readings are pretty accurate, as mentioned its hard to calculate the exact fuel consumed manually. Mine, I have a Stock A4 I get 19 in the city and up to 28MPG on the highway on Cruise Control
Pro
Joined: Feb 2014
Posts: 536
Likes: 2
From: Brisbane Queensland
Do you reset the computer each time you fill up? If not, then your 17mpg reading is a culmination of your ongoing fuel economy since the last time it was reset.
Or........ is it possible you made a mistake in the math?
I have an on board computer in three of my cars and although not always perfect, they do seem to be quite accurate.
Or........ is it possible you made a mistake in the math?
I have an on board computer in three of my cars and although not always perfect, they do seem to be quite accurate.
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Melting Slicks
Joined: Sep 2011
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From: The beautiful Alabama Gulf Coast!!
I've manually calculated my mileage only 3 or 4 times & it's always been very close to the car's computer calculation. I haven't reset the fuel mileage for at least a couple years now, and it's at 25.5 mpg average for what's pretty close to 50/50 city/highway driving.
Thread Starter
5th Gear
Joined: Jun 2015
Posts: 5
Likes: 0
I have a 99 Vette which according to the on board computer module calculates MPG at 17, however in reality it is about 10-12, which I calculated by dividing the mileage traveled by the amount of gas needed to fill the tank.
Any suggestions as to why the difference?I asked my mechanic if gas could be leaking while driving and was told no. What else could cause this difference?
Thanks
Any suggestions as to why the difference?I asked my mechanic if gas could be leaking while driving and was told no. What else could cause this difference?
Thanks
Pro
Joined: Mar 2014
Posts: 657
Likes: 181
From: Houma Louisiana
Thanks for the responses. I have set the trip counter 4 times after filling up and it continues to calculate at about 10-12 MPG. As of now I have driven about 110 miles and the fuel gauge is about half, which would get me about 225-250 on a tank of gas. Performance seems OK. Don't know what else to do.
Le Mans Master
Joined: Apr 2012
Posts: 7,816
Likes: 2,266
From: Brighton MI
Your mileage may vary...
In my wife's '14 ATS, every single time I have manually checked the mpg vs what the DIC says, it is SPOT ON, within .1 - .2 mpg.
In my '12 Malibu, it is a lottery - sometimes close, sometimes +/- as much as 2 - 3 full mpg.
I reset both every fill-up.
I've never checked my Vette manually...the DIC typically reads high 20's on a tank. It will knock down low 30s on the hwy. I think this is telling me I don't use WOT enough...
In my wife's '14 ATS, every single time I have manually checked the mpg vs what the DIC says, it is SPOT ON, within .1 - .2 mpg.
In my '12 Malibu, it is a lottery - sometimes close, sometimes +/- as much as 2 - 3 full mpg.
I reset both every fill-up.
I've never checked my Vette manually...the DIC typically reads high 20's on a tank. It will knock down low 30s on the hwy. I think this is telling me I don't use WOT enough...