I know this has probablly been touched a few times, but, what are the ZDDP level differences between M1, Amsoil, supertech, Castrol, ect? How does this effect extended oil drains? I was recently told by my friends father that BMW now has 15k recommended oil changes in some of there cars, and they run on M1. It got me thinking as to how safe this can be, I have never run my m1 over 10000 miles, but would if i could. Thanks.