Thanks for the explanation, that's exactly what my question was about.
I guess piston engines "exterior" surfaces are cooled by air, therefore shock cooling at low power & aircraft high speed is a great possibility. Internally the engine is still cooled by oil.
As for turbine engines, it doesn't actually rely on air cooling, but oil. But can I say that turbine engine doesn't need "exterior" surface cooling like a piston engine cylinder does?