whether VW/Audi/Volvo or Mercedes. There are things like oil spray jets aimed to cool the piston crowns from the bottom and stronger designs of the rods etc. Unfortunately, the VW motors also put a much lower compression ratio (17:1) in their turbo models, which leads to hard starting when the rings begin to wear, but Mercedes didn't do this. Back in 1976 there was an article in _Road and Track_ which gave a very detailed analysis of the then-new Mercedes turbo motors, but I don't have access to the exact bibliographical reference from here -- it's all stored at home.