traditional way of calculating mpg : miles driven divided by gallons. I got 18.9 but on the cars monitor display it shows 22.0 mpg. why is that the case.

 

Is that the display "average"?

 

Also, you filled up the same place?

 

yup @ same place (Shell). Ya it average. but still that average is different than the traditional way.

 

Daily average will change every day. So you're figures are probably correct.

 

I noticed on 500 day trips (done several this year) -- Which is usually a tank (I always fill up at 1/4 tank) -- the compture average is 1-3 MPG less than what it actually is when doing the math at the gas station.

Averaging 33 MPG highway after the PCV service. 26-27 Combined (50/50 hwy/city) 22-24 city.

Reading in the owners manual I recall that the average in the computer read out is based on the prior 50 miles of driving, not the total average of the entire tank of gas.

 

hmmm interesting ..so i guess every time i fill up full tank i should also reset the trip computer