The viscosity of biodiesel is low and I don't think the engine will hold up without additional lube. I don't think it's a good idea to use significantly less than 20% after crunching some numbers this morning. I was hoping we could go lower, but I know that the exhaust in my four strokes on 20% oil etherless is dry already. There is a property of lubricants called lubricity that is the ability of the lubricant to reduce friction other than it's viscosity. The problem is that there is no standard method of defining lubricity.

Andy, how much of your soybean oil was burning? Are you sure it wasn't just the ether burning? I don't remember a post with a run on straight soybean oil? Post 234 is what I'm referring to.