ICE turning on for a short time - bad or they know what they are doing?

Yeah, when the battery appears to run out and the ice fires, it still uses a lot of battery and software controls the ice load.
Same thing on the highway.
No worries, it’s a phev and all situations have been accounted for

 

Depends on the weather of course, but if if it consistently fires on a regular basis and doesn’t complete warm up, I would hit hv during the drive, then switch back.
But idk if it really does any damage in

 

How much damage do you suppose there would be? They're on the hook for a mechanical warranty here, so there's a very, very good chance they've already got this settled.

Toyota didn't bring these engines through a timewarp from 1950 or anything... Modern designs are much more tolerant of cold starts and short runs.

 

Otoh, I wouldn’t say the same for gen 3

 

What is it that makes you think that a 3 minute run is bad for the Prius? Is it complaining in any way? Are there error codes on the display?

Maybe this will reassure you... My first Prius (2002 gen 1.5) turned on the ICE every time I started a trip, and it cycled on and off till I reached my destination. My second hybrid was a 2010 Camry, and it would back out the the driveway on battery power, then start the engine as I shifted into drive. Both cars were driven in excess of 170,000 miles with no adverse effects.

Modern cars with modern lubricants and fuel injection are not as liable to break down as our grandparent's Ford. Just drive it and enjoy it.

 

Both those vehicles brought and kept the engine up to operating temperature

 

Quite true. Now compare the two designs HV vs PHEV. My 2002 would run the engine for the first 5 minutes whether I needed it or not. If I was just making a run to the store the engine would not reach full temperature on either end of the round trip. Every day the engine had to endure the shock of a cold engine start twice. His prius prime also has to endure a cold start twice each commute day.

I've never seen signs of moisture in the oil of my Toyota hybrids. I change the oil frequently.

 

The very fact that you're thinking about these situations and posting about it means it's at least somewhat concerning to you; so, when you know you're going to exceed the EV range anyway, there's nothing wrong with switching to HV during a steady-state portion of the trip and have the ICE activate and reach operating temperature under minimum stress.

 

You might try using "EV Auto" mode and see if that behaves differently. When I experimented with it in cold weather it ran the ICE for a couple minutes at the start of the trip even though it was using the battery to power the car. It could have been to use engine heat for the interior or to warm the engine so it would be ready to power the car, I'm not sure.

The Prius Prime engine is designed to warm up very quickly so it may not have to run very long before being used under load. The coolant circulation pump is electric and doesn't run until the engine reaches temperature. Also there is a heat exchanger in the exhaust that uses exhaust heat to warm the engine quicker as well.