So, I work as a Stock Engine Rebuilder in Germany, mostly with newer Engines. Outside of Diesels and some Old Stuff, the Number of Petrol Engines with Iron, wether Forged or Cast, I know is extremely Small, except for some Mercedes’s.
Pretty much all Petrol Engines I get to put together has Aluminium Pistons. And even a whole Bunch of Classic Economy Cars, like Opel Kadett, Fiat 500 and 2CV use them.
What is the best ingame Equivalent to Aluminium Pistons? Can’t be cast, as they run a lot cooler, which is why they are so common in modern high Compression Engines, and they can’t be forged, because they are lighter and less Tolerant to extreme Torque.
In my Experience they are the most common Petrol Piston out there.