I went pick up some oil for the Seadoo's and they didn't have the correct type at the time. The guy at the desk said it was ok to use 10W30 of your favorite brand of motor oil. This controdicts what the owner manual states. It states I should use 10W40 that meets API service classification SG, SH, or SJ. The oil that I use for my vehicle is Castrol GTX 10W30 which exceeds: API service SM/SL/SJ/SH. Can anyone explain this in layman's terms? I have a 2003 GTX SC and a 2006 GTX Wake. Thanks