Displayed average MPG

This is what you would expect if the battery provided some of the power. The car in HV mode will never get 280 mpg, so the extra range came from the battery.

The car divides the total miles traveled by the fuel used and that's the displayed mpg. If the battery is providing power, gasoline use drops and mpg goes up.

You are correct in that the calculation does not include the energy of any electricity used. It calculates using the gasoline burn only.

 

Electricity doesn't come in gallons. Traveling X number of miles on Y number of gallons yields X/Y miles per gallon. Other than on long road trips where I can't charge, I'm averaging close to 400 mpg.

The only meaningful metric is cost per mile. For that, you need to also track your electricity consumption from the wall. Easily done with a Killawatt meter.

 

Yap, mpg displayed on PRIME is mostly meaningless if you charge your traction battery and use EV mode to drive. There is no easy way to monitor HV only mpg on this car. I intentionally do not charge the car and drive a full tank purely on gas only in HV MODE to get accurate HV only mpg from time to time, like when I change to new tires.

 

I consider 80 low, for you and spouses driving it sounds right. I have manually computed and compared my mpg and they compare favorably. Extended EV driving can show incredible results sometimes. Everything always returns to mean tho, whether it’s stocks or mpg.

 

what it should display over a trip of mixed energy source driving is mpg's based on hv distance travelled and gas used, and mpk (miles per kWh) based on ev travel, and kwh used.