Its weird the trend seems decreasing to LA but increasing on return.
Perhaps through usage, car get to perform better?
On the forward journey, car gets to burn bad stuff. Then on return, it performs at its peak. After returning, its mostly idling - I just drive once a month to make sure. But does it take 350miles to get the car into peak performance? Maybe I am wrong - there is some other explanation.
I wouldnāt worry too much yet. Just different driving conditions, I assume. Lots of variables. Wind, traffic, driving speed, etc. The graph looks somewhat consistent, really, with a couple of low mpg outliers. As long as the mpgās donāt drop to the low end on a consistent basis, I would chalk it up to driving conditions. If the mileage does drop and stay low, you most likely will get a check engine light if it is an engine issue or sensor out of range.
Thank you - appreciate it. Merry X-Mas.
Merry Christmas to you too. If the mileage does go to the low end of the spectrum and stay there, report back and weāll help you investigate further.
I donāt believe that I have seen anyone mention the possibility of changing gasoline formulations, or even of a gas pump out of calibration.
I believe that the reason for drop in mpg is because that the car was not driven. It was a spare car but not anymore. I also noticed a pattern of low mpg after non-use of the vehicle. Treating with fuel additive brought it back right away.
I think you just donāt worry about the mileage. I used to get better mileage on the 200 mile trip to school than on the return. Too many variables to worry about.