Average MPG Reading Oddity

So I came home last night and the MPG screen showed 19 MPG. Got up this morning cranked it backed out of the drive way, 14.4 MPG??? WTH??? Any reason why that would happen? The only "changes" are tires were rotated Saturday (dealership reset the service notice), put rock sliders on it Sunday, temperature outside was 14 degrees this morning.

 

MPG resets when battery disconnects, maybe low voltage in the temps

 

yeah it's probably time for a new battery had not thought of that

 

Must be a long driveway. lol

 

It's not your battery. What he meant is that when you turn the truck off, it resets the MPG calculation. It's averaging fuel consumption over distance. The shorter the distance interval, the more inaccurate average is.

 

My '22 does not reset MPG when I turn truck off/on, on the dash display - Just keeps going off what it was when I last ended my trip
Only time I've noticed full resets is after filling up on gas and when disconnecting battery (while doing electrical work)

 

I could be wrong. I rarely look at the MPG display, but I have noticed it is highly inaccurate on short trips and also is highly dependent on the type of driving I have been doing. It's not like MPG is a constant. In any case, I stand by assumption that a bad battery is not the culprit.

 

So I think it's the cold temperatures after checking a few things

Cold weather and winter driving conditions can significantly reduce fuel economy. Fuel economy tests show that, in city driving, a conventional gasoline car's gas mileage is roughly 15% lower at 20°F than it would be at 77°F. It can drop as much as 24% for short (3- to 4-mile) trips.

Our winters have been so mild in the past I never noticed, but this year temps have been lower than normal for longer than normal.