Yamaha did it again. That oil - Yamaha OEM Yamalube 2M Marine 2 Stroke Engine Oil (sold in gallons) designated as LUB-2STRK-M1-04 is the best. I tried every oil on sale and that oil has smallest amount of smoke of all. Amazing it is mineral - as stated on label, but smoke less than Synthetic Penzoil. Just amazing. Cost more. Of course it depends how particular the engine worn out, piston rings and cylinder walls, pistons, premix or injected. But anyway it will keep 2 cycle engines alive for some time, happy me.