Welcome to Prius Chat. I believe you might have better luck if you ask this question in the plug in forum. Here's the link. Toyota Prius Plug-in | PriusChat Best of luck to you
Go to EV Driving Ratio screen. Take the gas miles divided by gallons consumed. In this example screen, 2,202 gas miles / 37 gallons equals to 59.5 MPG.
Every time I fill up I reset the odometer I then take the number of total miles driven and divide it by the 8 gallon It's an 8 gallon tank. I do this before the next fill up
Since that includes electric miles, the result is not fuel economy but rather "gas consumption". PiP calls it consumption MPG. To get gasoline fuel economy, take only the gas miles and divide it by 8 gallons. Ditto for electricity fuel economy, electric miles divide it by kWhs.
Simplest method, works for me, bullet-proof, and will circumvent the absurdly optimistic mpg indicators built-in.: 1. Fill tank. Note odometer reading. 2. Drive until it's running low, as much as you're comfortable with. 3. Fill tank. Note odometer reading. 4.Subtract first odometer from second. 5. Divide the resulting distance by the gallons of gas at the last fill up. Comments: a) How low you run the tank is arbitrary, no need to run it extremely low. b) Using consistent fill technique will help avoid vagaries in individual tank calculations.
The Prius plug in gas tank capacity is 10.6 gal. (40 L, 8.8 Imp.gal.) Ref link; http://www.toyota.com/t3Portal/document/om/OM47787U/pdf/sec_06-01.pdf
For future reference, any time you hear something per something else, the "per" indicates that you divide. In this case Miles Per Gallon, or miles divided by gallons. It's one of the most useful mathematical ways to determine the relationship of 2 or more things. I often calculate calories per dollar, or calories per weight or volume to maximize my food purchasing power.
Unless the grid electricity is translated into gallons, hence - MPGe. When I am calculating my food purchasing power I am not calculating it based on Carbohydrates calories only.
Yeah, the OP asked about MPG, which has nothing to do with electricity. Only 1 post from them, so we don't get a clarification to their question. ...and I don't count my calories, I just eat them. My preference is to eat them as proteins and lipids, but those are usually more expensive than carbs. Some people live to eat, and others eat to live. I'm the latter.
Then leave out the electric miles from dividing with gas gallons. MPG means fuel economy of gasoline, nothing to do with electric miles driven with electricity. I think you are referring to "consumption MPG" (not fuel economy). That's the total miles driven with gas gallon. PiP clearly differentiate that on the screen. There is no need to calculate. Which is why I think OP was asking gas fuel economy. That needs miles driven with gas.
the o/p's question was answered in post #3, as is usually the case in these tangent threads. he probably got what he wanted and moved on.