George,

Only time will tell, and I'll be happy to report any problems, but I'm betting on advice from people who claim to have been using "motor" oil in place of castor for years.

Castor's big claim to fame seems to be that it retains its viscosity and film strength as temperature increases. This property doesn't come into much play in a properly adjusted small diesel because of the greatly reduced operating temperatures. I found a performance comparison chart on the internet showing that castor does indeed perform as claimed. . .and is superior to even synthetic "motor" oils at high temperatures. However, for an engine that produces temperatures at the head/cylinder junction not much in excess of 220F, there doesn't seem to be any advantage to running castor. At the low end of the operating temperature range, the curves for castor and similar viscosity petrolium oils are essentially identical. If you try to operate a model diesel engine at the temps where the castor advantage kicks in, you're about to have larger scale problems that castor won't solve.

Since my FP wasn't designed for diesel, it might fail, but I'm betting that if it does it will be as a result of bending the con rod or snapping off the crank pin. . .I don't expect to see any galling of the bearing surfaces or cylinder wall damage unless I have a senior moment and run it overcompressed. To tell the truth, I wouldn't be as boldly experimental if I were running a $200+ USD purpose-made .40 diesel. But at the level of fuel consumption and the basic cost of a .40 sized plain bearing conversion head engine, the 9:1 price differential between castor and a name brand 20W50 in quart quantities and the 2:1 price differential (including shipping) between commercial fuel and my homebrew will more than pay for any wear or damage if I'm wrong about my lube.

Now, if I could find a consistent and predictable replacement for ether (*!@#! druggies), which was the original intent of this post, I'd really be in hog heaven. The starting fluid alternative seems to work, but now I notice court cases where they're getting convictions on meth labs based on the presence of empty John Deere starting fluid cans. So how long will it be before the manufacturers dumb down the ether content or simply stop making the stuff is anyone's guess.

Are there alternatives to ether? Xylene? Ethyl Acetate? Is anyone up on their chemistry? As a safety note here, I'm NOT advocating that anyone simply go out to their garage and try this stuff!