Bad mpg
Thread Starter
Racer
Joined: Dec 2014
Posts: 277
Likes: 10
From: West Palm Beach FL
Bad mpg
I just bought my vette a few months ago and have been noticing i am getting terrible gas mileage. The car is a 99 vert 6sp with 80k miles. Acording to the DIC i have been getting between 18-22 mpg. In reality i am getting 16-18 if i divide the miles driven by the gas consumed at each fill up. I recorded the best mpg so far yesterday at 18.2mpg about 260miles with 70% hwy driving and the rest normal city with no spirited driving. The tires are all at 35psi and i dont ever run with the AC on. Also the car is stock besides a zip tie mod intake.
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Could be something like a dirty air filter, bad plugs or wires, etc. And your tires should be set at 30 psi cold. Those are some things I would check out first.
Safety Car
Joined: Sep 2007
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From: Sunniest city on Earth
What fuel are you running? How does the car behave?
Safety Car
Joined: Sep 2007
Posts: 4,168
Likes: 21
From: Sunniest city on Earth
Granted, I had just fueled up and reset it, so that was the average between the gas station and my house, but amusing nonetheless
I've gotten 26mpg or so on longer drives, even with the mods
Le Mans Master
Joined: Feb 2012
Posts: 6,644
Likes: 479
From: OK
You may have bad 02 sensors... clean air filter, good clean cats, working 02 sensors, properly inflated tires, clean MAF sensor, good wires and plugs, clean properly functioning fuel injectors, and you should get optimal fuel mileage.
I would add some Sea foam to my next tank of fuel... clean the MAF, replace 02 sensors, plugs and wire, see if that helps.
Someone may offer help on how to test your 02 sensors..
I would add some Sea foam to my next tank of fuel... clean the MAF, replace 02 sensors, plugs and wire, see if that helps.
Someone may offer help on how to test your 02 sensors..
Last edited by 73Corvette; Mar 22, 2015 at 08:17 AM.
Racer
Joined: Nov 2012
Posts: 376
Likes: 21
From: Coos Bay Oregon
Are you pulling any codes? I would start there. Also, are you leaking any gas. Do you smell gas as you slowly walk around the car? At 80K miles, you could be needing plugs and coil packs. Those are normally part of the 100K mileage check, but things happen. Pull the codes first and see what the car is complaining about.
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It could be that the odometer is off slightly if the rear tires are not the correct size, but that shouldn't be a big variance in the computation.
Driving style especially with a manual trans can make a difference in mileage. Staying a little too long in a lower gear or up-shifting at a higher RPM can easily result in poor mileage over a period of time.
Melting Slicks
Joined: Mar 2013
Posts: 3,311
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From: Toronto Ontario
The gas gauge wouldn't be an issue as he has checked mileage the "old-fashion" way. Divide the miles driven between fill-ups by the number of gallons of gas shown on the pump meter.
It could be that the odometer is off slightly if the rear tires are not the correct size, but that shouldn't be a big variance in the computation.
Driving style especially with a manual trans can make a difference in mileage. Staying a little too long in a lower gear or up-shifting at a higher RPM can easily result in poor mileage over a period of time.
It could be that the odometer is off slightly if the rear tires are not the correct size, but that shouldn't be a big variance in the computation.
Driving style especially with a manual trans can make a difference in mileage. Staying a little too long in a lower gear or up-shifting at a higher RPM can easily result in poor mileage over a period of time.
My gas gauge issue is creeping back up since I stopped using fuel treatment and that is exactly what happens, the gas gauge drops faster then it should and shows your empty when your really not, so its impossible to get an accurate reading of your mileage.
Le Mans Master
Joined: Feb 2012
Posts: 6,644
Likes: 479
From: OK
Doesn't matter where the gas gauge is... your dividing the number of gallons into the number of miles put on since last fill up. Gas gauge has nothing to do with it. Fill it up till the pump stops,,,drive, refill till gas pump stops... divide miles driven by gallons of gas pumped.
took 10 gallons to fill up, you drove 100 miles...10 mpg
The gauge could be reading wrong but, that doesn't matter.
took 10 gallons to fill up, you drove 100 miles...10 mpg
The gauge could be reading wrong but, that doesn't matter.
Pro
Joined: Feb 2014
Posts: 536
Likes: 2
From: Brisbane Queensland
Yes but hes measuring the mileage driven based on the gas gauge going to E and hes thinking the tank is empty, which in my case and MANY MANY others that was not the case.
My gas gauge issue is creeping back up since I stopped using fuel treatment and that is exactly what happens, the gas gauge drops faster then it should and shows your empty when your really not, so its impossible to get an accurate reading of your mileage.
My gas gauge issue is creeping back up since I stopped using fuel treatment and that is exactly what happens, the gas gauge drops faster then it should and shows your empty when your really not, so its impossible to get an accurate reading of your mileage.
Distance (miles) divided by fuel used (gallons) = MPG
What part of that equation don't you understand?
Thread Starter
Racer
Joined: Dec 2014
Posts: 277
Likes: 10
From: West Palm Beach FL
The gas gauge wouldn't be an issue as he has checked mileage the "old-fashion" way. Divide the miles driven between fill-ups by the number of gallons of gas shown on the pump meter.
It could be that the odometer is off slightly if the rear tires are not the correct size, but that shouldn't be a big variance in the computation.
Driving style especially with a manual trans can make a difference in mileage. Staying a little too long in a lower gear or up-shifting at a higher RPM can easily result in poor mileage over a period of time.
It could be that the odometer is off slightly if the rear tires are not the correct size, but that shouldn't be a big variance in the computation.
Driving style especially with a manual trans can make a difference in mileage. Staying a little too long in a lower gear or up-shifting at a higher RPM can easily result in poor mileage over a period of time.
Le Mans Master
Joined: Feb 2012
Posts: 6,644
Likes: 479
From: OK
Thread Starter
Racer
Joined: Dec 2014
Posts: 277
Likes: 10
From: West Palm Beach FL
Melting Slicks
Joined: Mar 2013
Posts: 3,311
Likes: 384
From: Toronto Ontario
Doesn't matter where the gas gauge is... your dividing the number of gallons into the number of miles put on since last fill up. Gas gauge has nothing to do with it. Fill it up till the pump stops,,,drive, refill till gas pump stops... divide miles driven by gallons of gas pumped.
took 10 gallons to fill up, you drove 100 miles...10 mpg
The gauge could be reading wrong but, that doesn't matter.
took 10 gallons to fill up, you drove 100 miles...10 mpg
The gauge could be reading wrong but, that doesn't matter.
I was just very confused by my gas gauge issue I thought maybe he could be dealing with the same thing, but I guess not.
shhhhhhh, stop chirping grasshopper.
