You are all assuming that the contaminents, water, alcohol, and acids penetrate and pass through the film strength of the synthetic oil. I say it doesn't. One of the main reasons an awesome synthetic like Amsoil 15w40 Heavy Duty Diesel and Marine Oil works so well. Sincerely Randy (Cap'n) Hook '63 ragtop 84/pg '65 monza 4dr. 110/pg