I originally thought it worked as good as a petroleum-based oil, but it doesn't, plain and simple. I've found some dirt in the boot and carb intake twice now, and I resealed the airboot with weater strip adhesive TWICE just to make sure I wasn't letting dirt in somewhere besides the filter. Then I switched back to my old oil (Silkolene filter oil), and I haven't had any problems. Seems to me No-Toil is decent, but not good if you want 100% protection. It also lets water in the filter, as I had dirt that was pulled in by water and dried out on the inside of the airboot. This most likely occurred during washing, but I don't have any of these problems with regular filter oils. Just beware if you are using No-Toil. I don't think it works too well in wet riding conditions.