I never found that claim of lubrication for D-Star. I have read about the lubricity concerns with the new ultra low sulphur diesel fuel in the US. The stores everywhere stock diesel fuel additives for older engines since the introduction of the new diesel fuel. The link you gave said most of the tests were successful. There is also a significant difference between a Mil-spec application and a hobbyist application. I'm sure you do understand that any failure in the military is a seriuos problem. At my last job in the hobby industry we always joked the customer would smash the product into the ground or otherwise destroy it long before it's useful life was over or the warranty expired. I have found this to be true of most things in the hobby industry. There is no single component that will be lubricated entirely by kerosene in any of our engines. I don't think anyone here is advocating elimination of the lubricant completely. I think the problem is more closely related to crankcase oils in long term applications where a dilutant with a high boiling point will never boil out of the oil reserve and cause lubricant failure. I have read about such failures in diesel engines with faulty injectors.

With 20% castor oil I expect no problems with the four stroke engines in terms of longevity. I was going to try reducing the percentage to see if problems arise. As soon as I get the chance again I'll be running engines.

My engines have been run mostly on [link=http://www.maximausa.com/products/2stroke/castor927.asp]Maxima Castor 927[/link] at 20%, regular kerosene at 78%, and 2% octyl nitrate (2-ethylhexil nitrate). I have also tried various crankcase oils and two stroke synthetic lubricants. The engine is warmed on regular model diesel mix or heater, pior to running on etherless fuel at this time.

I guess I don't understand the concern. You make it sound like none of the the kerosene evaporates. We do know that most of it is burning. If the residual oil mixture in the crankcase of my engines was 50% kerosene, I would be surprised. Even if it is, the viscosity of the resulting oil mixture is suitable for the engine in my opinion. Now, I have to figure out how to determine how much kerosene is in the lube. I might be concerned with a two stroke, but Treven's experience says otherwise. Also how is the situation in a glow engine? We did go into these tests blindly, but experience has shown that it seems to work. Either we are on the verge of destroying our engines or the concern isn't really a concern. The truth may not be easily known without strictly controlled tests, possibly beyond our hobbyist capability. The easiest test would be to reduce oil content until problems do occur. This would tell us in practice what the engine needs to survive, even if we don't really know what is happening.

I suppose a good way to test would be a separate lube system, and straight fuel. This would let me determine the dilution easily.