I just called Chevron, and he said i shouldn't use the SL Delo 400 15w-40 in my wet clutch because it now has friction modifiers in it. If is says ci-4 plus, it has friction modifiers in it. He also said the Supreme line will not work also. Even the 10w-40 and 20-50 have friction modifiers. I have been using Shell Rotell 15w-40 and it is also rated Ci-4 plus, but has been woking for the last 600 miles or so. Chevron said we will be stuck using the OEM stuff from now on. I "might" try the Valvoline 10w-40 next.