Trip Odometer Accuracy???

A related question: My brand new Prius Prime odometer reads 290 miles, at 75.6 mpg. Now this started out much higher, and I assumed it just had a lot of EV miles included in the 104 miles on it when I drove away. I calculate 3.78 gals overall. But, surprise: the trip A reads 288.3 miles at 58.7 mpg, for 4.91 gals. How can trip A use more gas than the total used by the car?

 

So, for the first 290 miles the car got 75.6 mpg (minus the built in 5%-7% optimistic error). Over the last 288.3 miles it got 58.7 mpg (minus the built in 5%-7% optimistic error). The only real way to know how much gas you've used is to fill the tank and even then you'd need to know it was full when you started. Any calculations from the data available right now would not be very dependable especially when dealing with such a small sample.

It does seem to me that you got the car with a fully charged traction battery and have not charged it again. I don't know what else would account for the extreme drop in fuel economy.

 

One possible explanation for the discrepancy in mpg between the ODO and TripA is that sometimes during the first 104 miles, the fuel consumption corresponding to ODO was reset. Newly reset fuel consumption for ODO include more EV driven miles than the trip A has.

 

Trip A used more gas than the total used by the car per the odometer. Trip A is included in the odometer, but used a gallon more gas!!!
Salamander, do you mean that the odometer mpg is not valid compared to Trip A? Score 1 for the marketing dept. if so.

 

They both are valid. What I am guessing is that someone reset the Odometer mpg before you bought the car during the first 104 miles registered onto the car. MPG corresponding to the ODO is resettable but ODO itself will not reset. When you do, the mpg will be from that reset point on. So, say someone reset the mpg corresponding to ODO at 100 miles, then you buy the car at 104 miles and drives 186 additional miles. ODO now reads 290 miles, but the mpg displayed is for the last 190 miles driven since the reset point. In comparison, the Tripmeter mpg is always for the distance traveled for that trip until reset. In your case, the trip A reads 288.3 miles, so mpg corresponding to the trip A is for 288.3 miles of the drive.

See the cutout from the manual below.