Heck I use a few gallons of bar oil a year. If you go to walmart you shouldn't have to go out of your way to get marine two stroke oil, which is tcw3 oil? Just buy you a qt of super tech marine oil. Or if you have some around put it in. I put it in every 5 gallon jug I buy. I I miss a tank I don't worry. I add what I need and if I think about it when I get some I just dose the tractor tank. I don't are if some is already mixed, as when I added pure diesel it diluted it, yea it will still be richer than needed but again I don't worry much about that.