MPG display difference?

Josh, let me explain...
"A man with one watch knows exactly what time it is. A man with two watches never knows the exact time."
My advice? Turn one off.

 

Yep this is what I do, except I use Excel to correct for tire size difference (OEM Goodyear Adventure is 682 revs/mi. My 32" Duratracs are 657 revs/mi).

Even greater precision can be obtained if you keep using the same pump at the same station (reaction times for the automatic shutoff when full can vary among pumps), but that is often impractical.

 

Similar topic, but why does the trip MPG calculate based on time since start up, rather than the trip set via the odometer?

 

Divide the miles traveled by the amount of gallons it took to refill the tank. See if your numbers really match up. Now you have 3 different numbers

 

The one on dash is per recent tank average since refueling. As for the one on the radio screen I know for a fact it’s not a lifetime average. Reason I know this is I haul my tractor and heavy attachments on a 20’ car hauler trailer. When I haul this much I get just barely over 10 mpg. After one tank the radio mpg reading drops from 17 to 13mpg for example. Would take much more than one tank of fuel to drop it that low if it were over a long span.

I believe it’s the last 1000 mile average myself just by how the numbers change so dramatically. Could be very wrong but it’s definitely not overall average of consumed fuel since a reset for the truck as I never reset mine.