To make this even more frustrating, there is not an engineer on this planet who wouldn't design the logging of EV vs. ICE into the vehicle computer. Most importantly, the knowledge of ICE usage
should factor directly into the service intervals
(but it doesn't seem to, per much discussion elsewhere in the forum). One of the most relevant threads on bogus oil change interval is
HERE.
Still, I am willing to bet that there is a TON of diagnostic information available that just hasn't been exposed in the user interface. Options for additional information include the Hidden Diagnostic Menu
HERE, Honda's HDS tool, What may be available through the ODB 2 interface, etc.
I think KentuckyKen has even gone so far as to install an hour meter on the ICE (I love the ingenuity) !
Until a better way is discovered, I plan to track every drop of gas, and every kWh of electricity I use (My L2 charger logs kWh). That way, the mileage breakdown would be something similar to this:
EV miles ~= Total kWh * 3.25 [basis: 31 kWh per 100 miles]
ICE Miles ~= Total Gallons * 45 [basis: 45 MPG when running on gas]
This can be compared to total miles on the odometer as a sanity check, and maybe these approximations can be refined a little.
My numbers (so far) :
Odometer = 1093
EV = 293 kWh * 3.25 = 953 miles
ICE = 4.2 gal * 45 = 189 miles (8 bars remaining out of 20 on 1st tank of gas)
I am happy with this correlation so far with very early experience.
I plan to connect to the OBD2 just to see what comes out, but without additional technical details, I am pessimistic about getting additional useful information directly from the vehicle.