All electric miles v. gas-miles data on 2017 Prime?

No, there is no mile information on display that will tell you the actual electric driven miles vs gas driven miles. However, if you look at the Drive Monitor on MID, as long as you have not reset the record, the one that corresponds to ODO will show the EV Driving Ratio. This is the ratio of electric driven miles vs gas driven miles since reset, (if never reset then it is for the entire ODO miles). Note that this is not the ratio of EV mode driven vs HV mode driven. This ratio include the EV portion of drive under HV mode counted as EV driven miles. I think that is exactly what you want.

However, for the purpose of oil change, I recommend just sticking with 10K miles or 1 year whichever comes earlier regardless of the miles you have driven on electric or gas at least 5 years/60K miles on ODO. Engine and power train components are covered by 5 yeas/60Kmiles warranty. On unlikely event you need this warranty coverage, you maybe asked to show the service record of Toyota recommended oil changes on 10Kmiles/1yr interval.

 

Of course, there is the old fashion way. I keep a small notebook in the door panel. When I add gas I note the date, mileage, and number of gallons. I add gas roughly once every three months, usually about eight gallons. Over a year, that might be 32 gallons. I know the car gets roughly 50 miles per gallon, so in an average year I will have driven 1600 miles with the ICE. Not high tech, but good enough for an 80 year old driver. I also realize that many of these miles were just the last mile or two to get home, so the engine never really got up to operating temperature. So I have no problem changing the oil much earlier than I would with a normal car.