Nearly swallowed my tongue yesterday. Was talking with the previous owner about his new boat and he said he was going to change his oil. His new boat has the same engines as mine, 12v71TI's and he was using Delo 15w40. Told me he used it in my boat as well. My oil only has about ten hours on it. I explained that DD is very clear about what oil to use in the two stroke. But.....he wasn't convinced. Anyway, when Detroit reopens on Monday I'll get twenty gallons of DD 4oW and do a change.