One more oil change interval post

The unused oil may oxidize a tiny bit sitting in the bottle, but no where near the rate of oil heated up in the engine. The engine protective additives in the oil aren't used sitting there. So just use it next time.

Your engine is doing the equivalent of short trips, so I would just stick to the 10k miles.

Engines go through a lot of testing during development. From that, GM knows how quickly an antiwear compound is getting used up under different running conditions. Their oil life monitor uses that data to calculate oil life. It generally called for a change my Chevies around 7500 miles. The longest it would go is two years in a Volt.

The one I paid attention to turned over at 10k miles.

A car's warm up cycle is more about the catalytic converter and reducing emissions. getting to the efficient point helps with that, but that happens before the oil fully warms up to the point all the water is boiled out.

If the oil still looks clean, I'd used it a lawnmower, or even another car. I've used old oil as bar oil for a chain saw.

 

If I know I am not going to make it on battery alone, I will usually turn the HV mode on with 8% on the battery and ~2.5-4 miles to go on the highway. When I enter the offramp, I take my foot of the accelerator and the ICE turns off, the regen turns on and by the time I get to the light I have the needed 10% to get home in EV mode. It seems that 2.5 miles is enough for the computer to allow the ICE to turn off.

Most of the year I can make it all the way home on EV mode. Every once in a while I will miss calculate and the ICE will turn on as I pull into the parking lot. Then I will sigh and just shut the car off. Sounds like it would be better to just keep the engine on while parked until the computer shuts it off.

 

If you have time, that's probably the way I would do it or simply switch to HV mode when cruising at highway speeds. Added benefit is heat in the cabin. I've been doing that this winter and my mpg hasn't gone down as bad as last year - but last year was colder.
Good Luck....