I have a 2017 PHEV and when the ICE starts it first runs at high Revs and is not engaged to the drive train until oil is circulated. This is probably true for HEV's and most normal ICE cars. The engine gets to idle for a few seconds to circulate oil before a load is applied.
Take the worst case for the PHEV, when the PHEV is thrown into Sport mode up a hill the ICE is required to start without many Revs. This is where I found a problem with my camshaft sensors, I got code for misfires and sensor position. A rough engine note was heard and obviously the engine management light appeared with the codes for the above warnings. The sensors supply a digital signal to the engine management system and control the sparks, valve timing etc. Injectors were swapped with little change. Spark plugs were changed and the car was good again but the plugs had probably accumulated excess fowling. The sump oil smelt of petrol, again maybe unburnt fuel because of bad ignition. Not long after (100 miles of ICE only) a camshaft sensor circuit fault appeared. Both inlet and exhaust camshaft sensors were changed. Possibly a bad batch but there have been a few on later models. No errors in the last 2 years.
As the PHEV only runs the engine from cold and for short periods for heating or short range increasing distances, the effect is more pronounced. I run my PHEV with super unleaded for the extra cleaners. That's £0.50 blown each month on the UK gallon the cars uses
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I still hear a split second of the engine finding it's timing.
I also run the car in HEV mode each month to the point where the engine is hot to clear any condensation that will build up in the engine. A quick check of your engines dipstick and the underside of the oil filler cap will show this condensation. This appears as a sludge mix of water and oil. Worst case is that this sludge collects in your internal oil ways and around the camshaft sensors that need a nice clean gap. This will not be there if your engine gets hot on each journey.
