Must I use the gas??

i would only keep a few gallons in it, and run through it once a year

 

You should have bought a EV instead of a PHEV. Since you have a gas engine, you still need to run it periodically and do all the maintenance (oil, filters, coolant, etc.) you've done with all other gas cars.

 

+1

It is a little curious that you're hauling around hundreds of pounds and ten thousand of dollars worth of drive train components that you don't want to use - and let's face it.
It's not like you're going to be taking any weekend road trips in this car.
Put a half tank of gas in the car and run the engine every now and then to and keep the "change owner light" from illuminating in order to maintain the car's value.

 

Have you ever heard of the phrase "Use it or lose it"? That's what will happen to the gas engine side if you let it sit unused.
Try to keep the gas tank about half full and run your engine to full warm-up BEFORE shutting down, at a minimum. This should probably be done every other week, in your high humidity climate. You see how fast things rust around you; what do you think is happening to your engines' internals if they don't move?

Good Luck......

 

Do you have a regular, 5 day a week commute? In your shoes, I’d purposefully run it like a non-plug-in hybrid, using the engine, one day per week.

 

I've read recently that it takes a drive of 1 hour to properly heat the engine enough to keep away harmful buildups in the oil, plugs, etc.

 

That might be true for something older or larger like a commercial truck, but you can get a small auto engine as featured in your Prius through a full warmup in just a few minutes.

 

There's an exhaust gas heat exchanger to speed up the process and the ECU controls all the ICE operations parameters. Running the car for an hour, even in HV mode wouldn't help all that much - because the ECU controls how often and long the ICE will stay on. There's only so much you can do, when "Skynet" over rules you.

You can place the car into maintenance mode; but to me that's a waste of time and gas. Actually running the car and placing a "load" on things would work better - IMHO.