Also, the number of car manufacturers outnumber the number of car engine manufacturers - so if one company which actually makes engines (cough) optimizes their

Also, the number of car manufacturers outnumber the number of car engine manufacturers - so if one company which actually makes engines (cough) optimizes their engines for testing, several car manufacturers may be caught with their trousers down. (Which, I am sure, will lead to all sorts of interesting lawsuits.) For instance, the engine in cars as different as the Land Rover Defender (sadly, no longer among us) and the Volvo, say, S80 is basically the same Ford-engineered unit.