I've really had excellent luck with unheated WVO. I use good oil not cooked to death or thick or sludgy, with 2 - 5 % gasoline added. If my 3 main vehicles died tomorrow, the fuel saving would have paid for those vehicles 5 or 10 times over.

The 300 D, after 30 K + miles on unheated WVO, developed a condition where it starts fine, but smokes , and is kind of low powered until it gets up to speed. This happened after sitting over the winter ( i don't drive them in the winter),that's why i am thinking maybe stuck rings. I took the injectors apart, and apart from some minor crud in the pintel area, were remarkably clean inside.

The Diesel rabbit seems to need the block heater plugged in about 1/2 hr to start, this developed right after changing the fuel filter, and filling the new one with diesel purge. That vehicle has run only about 5 or 10 K miles on WVO, mixed with the bit of gasoline, and also kerosene in cooler weather.

I'm thinking of trying the Marvel mystery oil soak, esp. on the 300D.

Any thoughts?