Mileage question

[mtb9153]

I have noticed a pattern which has developed in my last many tanks of gas and I was wondering if others have seen this?  The first half of the tank seems to be much more predictable than the second half of the tank.  My last two tanks have really been my best as mileage goes with the first half staying right around 41 to 44average mpg.  With periods of jumping all the way up to the 47 range and then falling back into the 45's before slipping down into the 40 and 41 range with the second half of the tank.  I don't understand way the second half constantly seems to be less mpg?

[fotomoto]

My guess:   the fuel level sensor calibration is off for the second half of the tank.  I've seen this in other cars:  first 1/2=200 miles, second 1/2=160 miles, etc.

[Jus-A-CMax]

Mine is the opposite. Less MPG at the top quarter and then piling on the MPGs at 1/2 or less tank. Who knows...

[MacGyver]

Well, there's less weight from the fuel, but I think it's mostly a nonlinear fuel indicator, i.e., first half is less than half, that sort of thing.

[MacGyver]

[media]https://docs.google.com/file/d/0B_0HkVXu8lXNQmNnR3gwUXB5VlE/edit?usp=sharing[/media]https://docs.google.com/file/d/0B_0HkVXu8lXNQmNnR3gwUXB5VlE/edit?usp=sharing

 

Keep trying to post a pic, is there a tutorial on that or something, it should not be this hard...

 

I've got a question; my math, depending on which numbers I use for the trip mileage, would indicate MPG of like 66/75/123.333 here, but I'm baffled as to how it's showing 56mpg?

 

Am I not using the right #s or ... how is it arriving at 56 mpg? Anyways, my numbers are; distance, 19.8, 14.2 EV, and 3.0 regen.

 

Can someone please explain this?

Edited May 4, 2013 by MacGyver

[wab]

I have noticed a pattern which has developed in my last many tanks of gas and I was wondering if others have seen this?  The first half of the tank seems to be much more predictable than the second half of the tank.  My last two tanks have really been my best as mileage goes with the first half staying right around 41 to 44average mpg.  With periods of jumping all the way up to the 47 range and then falling back into the 45's before slipping down into the 40 and 41 range with the second half of the tank.  I don't understand way the second half constantly seems to be less mpg?

 

 

My guess:   the fuel level sensor calibration is off for the second half of the tank.  I've seen this in other cars:  first 1/2=200 miles, second 1/2=160 miles, etc.

 

 

Well, there's less weight from the fuel, but I think it's mostly a nonlinear fuel indicator, i.e., first half is less than half, that sort of thing.

 

yep

Yep

and YEP

 

I've noticed over the past few decades that car manufactures must use "new math" the

first half

always has more gallons than the

2nd half

even if you drive it tell it's empty.

[MADCMAX]

It is typical for the fuel gauge to go down more quickly on the 2nd half of the tank, many cars do this.  

But I have found that the car computer says  you used LESS gas than you actually do.  So you use MORE gas than the computer says, therefore reducing your MPG that the computer says you are getting.   I have been tracking my mileage (actual) and gas used (actual) only to find the 37MPG average is the norm.  I find that when cold outside it could be as low as 33mpg and when hot, could be as much as 40mpg.