I figure my own gas mileage tank to tank. Recently my gauge for average MPG read 38.8 and my calculation was 36.7.
It was high by 2.1 MGH.

Anyone else have this issue?

 

lol i think you mean

does anybody not have this issue

 

The only way I have found to correct the problem is to Engine Off Coast ...

Mine is nearly dead on ...

 

isn't there a search function to help stop duplicate thread? LOL

 

Mine reads 8% more than calculated FE. However, my odometer reads 3.5% high, so FE is somewhere between hand-calculated and displayed.

 

BUT guys, didnt we also have a thread recently discussing the ambiguity of exactly how much fuel is left in the tank when "empty" or "near empty"? I mean wouldn't you need to know how much fuel exactly you've already used to get correct calculations or am i missing something obvious? (and please tell me if i am)

 

No, you do not need to know the amount left in the tank to calculate fuel economy. You only need to know how much fuel you used. To think of it another way, to see how much money you spent this month, you need to know how much is missing from your bank account, not how much you still have left. You find out how much fuel you used by filling the tank back up. The amount it took to fill up the tank is the amount you used to go the number of miles on your trip-A meter. Those miles divided by the number of gallons it took to fill up is your fuel economy in MPG. As mentioned, though... my odometer is about 3.5% low, so I multiply my MPG numbers by 1.035 to give a more true MPG number.

 

I had an interesting one last time I filled up.

1/4 tank left according to gauge.
pumped 10 gallons in it.


So either I was BONE dry, or it overfilled. (and I always stop pumping one the pump stops) So it is possible that it will let us pump more gas in than we used. Over a longer period of time I can see this balancing out though.

 

Well, keep in mind that the tank gauge is nowhere near linear. With It drops to ¼ tank (2 bars left) at something like 60 miles remaining on my car... and that's with 345 miles on the tank already. So, according to its own math, it shows ¼ tank when only 15% of the tank is left. When you're down to 1 light (1/8 of a tank), you've only got something like 20 miles left (according to the display), so that 1/8 tank mark represents only 5% of the tank.

In other words, you had burned a lot more than 3/4 of your tank when you filled up. Be careful about topping off, though... you don't want to damage the vapor recovery system! $$$!!!

EDIT: You weren't bone dry. These tanks hold a little more than 10 gallons. Also, you can only put in more than you burned if you weren't filled up all the way on the previous tank.