TCW 3 is designiation for Two Cycle Water Cooled outboard engine oil, Royal Purple states this oil can also be used in pre-mix applications. This fashionation with oil amazes me, I might use 4 quartes a season. I suspect that I'm on the high side of many that post here. I've used Pennzoil, Belray, Amsoil, Yamalube and several others in a pinch. Been flying gas since 1989, engine failures were always the result of ground impact, never lack of lubrication. Good oil will not make a poorly constructed engine last any longer.