I have been buying the West Marine brand of oil and filters for both the gear casing and engine with no issues for the last 200+ hours. I have also been buying the fuel/water separator filters and in-line fuel filters from West Marine as well. My Yamaha dealer told me that while he wished I would buy from him instead, that it didn't void the warranty and that the oil and filters "technically" met the standards, the biggest concern was quality control of the non-name brand items. I can't believe that there are widespread issues, otherwise a store like West Marine would go bust. I have seen the way the watermen on the Eastern Shore who depend on their boats for their livelihood treat their hulls and engines, they certainly don't baby them the way we do, they run them hard and use what is cheap, and they keep going. I have the feeling that it is frequency of use, or rather the length of non-use that affects the engines.