I’m no expert, but Euro6 requirements have lead to problems with ICE, including hybrids. I grew up with my dad’s small country garage and occasionally helped the mechanic “de coke” the then relatively simple push rod petrol engines. Contaminated valves a common problem. He would have been horrified at stop start and hybrids running engines in short bursts, often from cold.
I turn off stop start each journey and re engage it when suitable – at traffic lights etc.
”Italian tune-up”. After a series of short, often congested, trips when traffic permits, l give it the beans in Sport mode, ensuring a number of visits to the red line – a modern day “de coke” and also clearing the contaminants from DPFs etc
Not exactly saving every drop of petrol, but avoiding some of the issues described. I like the concept of Nissan’s or Honda’s ePower, using a small Atkinson cycle ICE to generate electrical drive power, but some HEV and PHEV designs spell trouble for their ICE engines and 12 volt batteries in the long term, IMHO