Special grade 'motorcycle only' oils have higher levels of phosphorus additives which are superior wear lubricants. (These were taken out of car oils with the advent of emission controls.) You cannot use these in cars as they will poison the catalytic converter and/or Oxygen sensors.<br /><br />They should be fine for 4 stroke outboards without catalysts and O2 sensors.<br /><br />Unless anyone knows of a Bona Fide reason why these should not be used I intend to use the same 'M/C' oil in my Tohatsu as my Kawasaki.<br /><br />These phosphorus additives are not some 'Slick 50' gimmick - they are the best compounds you can use for engine lube oil, just are not compatible with emission catalysts etc. Do some Google research and verify for yourself:<br /><br />'Engine oil contains zinc and phosphorus in the form of zinc dialkyldithiophosphate [ZDDP], an engine anti-wear additive. The phosphorus from this additive is a catalyst poison because it tends to form deposits on the catalyst surface. FOCAS offers consistent oil consumption rates and characteristics. The main impact of non-thermal aging (phosphorus and zinc deposition) on the catalyst surface typically manifests itself as delayed catalyst light-off times and lower temperatures as the poisons tend to accumulate on the inlet face of the catalyst and block active catalytic sites.'
