I was told alot of newer outboards are reccomending synthetic as their mix of choice! I was using EXON superflow reg 2 cyc oil TCW 3 7 bucks a gal. but was informed all 2 cyc oils are not the same, some leave more residue than others. I was also instructed to use an additive to reduce carbon buildup in gas/oil mixes for outboards. Over all if spending a few extra bucks on a better oil reduces engine failure looks like I'm a synthetic kind of guy!