I've been keeping track how much gas I'm throwing in my tank and how many miles have gone by. It seems the MPG reads about 1mpg more than actual. When I compare the 'fuel used' with actual fuel used, it shows a bit less, which must be the cause for the MPG to be higher. I'm going to check it a couple more times to make sure this is the case.
Anybody else check this out?
Bill

Hi Bill,

Personally, I would believe the readout more than I would the 'actual fuel used'. The computer on our cars is reading the fuel going to the engine. It would be hard to actually go by how much gas you put in the tank. Not all gas pumps deliver gas with the same amount of pressure and they all cut off at different times. So that leads to me believing the computer readout more than the pump. How much gas do you actually put in the tank ... Do you stop when the automatic shut off stops the pump, or do you continue to fill the tank with a little more gas to top the tank off. I've noticed some gas pumps will let you put almost another gallon in the tank after the automatic cut off and on others, you're doing good to get another tenth of a gallon in before it's running out the filler neck!

I think to get the actual fuel used, you would have to use the same gas pump and top the tank off *exactly* the same way each time for several tank fulls to be accurate.

Just my .02 worth, but I tend to believe the car's readout more than anything else.

Don

The way I look at it, is you have to reset it, if your are going on the highway for instance. So you have the read out for that stretch of road only. Because once you reset it, and hammer on the gas it can go down to like 8.7 mpg, but even if you cruise for 5 miles after that, it will still average out at 11 or something.

Get my meaning? I think you have to reset the mpg if you want your current reading.

's

By all means, throw in a hypothesis then, Mr. Productive.

My assumtion was it just converts the gas used with miles driven, so its just a digital estimate. So if you want the mpg you have to reset it and drive sanely.

calm down.. :p i agree with most of the stuff if not all the stuff both of you said. if i affended you, im sorry.

I wouldn't trust the mileage it reads. I think the the reading is based on vacuum which is not going to give a very accurate reading.

I checked my milage by runnng thruogh a full tank, refilling then dividing miles driven on that tank, by gallons used to refill tank. I also found that my results were also 1 mile less a gallon than the cars reading. I think the car counts each revolution of the crank shaft to figure out fuel used because these revolutions are also used to control change oil light.

well i know how it works...thats the easy part.

just wondering how many other people have calculated it out and how off it was. seems 1mpg high is usual.

Mine is off by 1-2 mpg. The fuel used is usually low too (duh). I check it the old fashioned way and use the DIC for helping me save gas

Don't have that display...

my mileage is usually damn close, and when I go to fill up, if I'm bone dry in my tank, my comp says 16.2 galloms used, so I think that it has a small difference. the best thing to do is to know your car well, and figure if you drive the same for just about every tank of gas, then compare the diff from every tank, then take the average. or just wait till you're cruising and reset the comp and odometer at the same time to see if they are reading the same.