RCIGN1...good link, I found the thread and from what read his conclusion was to go with Bel-ray H1R and a 15% bigger fuel tank? It had less carbon buildup than the other oils. I've been using Yamalube semi-synthetic for years in snowmobiles and after 30-40 hrs use I pull the powervalves for cleaning. Yamalube is one of the cleanest of the few oils I've tested and it's anly about $16 a gallon. I wish I had a pile of engines and some tolerant neighbors.....