Are the Kuboto D750 Diesel's any more likely to build up oil sludge then any other engine, or is it purely a lack of maintenance by the previous owners? I changed the oil a couple months back of the 443B and the speed that the oil drained from the hose was rather slow. The oil was black and dirty, but the thickness was what you would expect for dirty oil. It wasn't thick like molasses. After putting the new oil in and running it the new oil went black rather quickly. At that time I wasn't sure if the slow flow rate out the drain hole was normal or if there was something blocking the hose inside the engine. I recently drained the oil again, the same thing, slow coming out the hose. Pouring some clean oil in and watching it drain out black tells me there is sludge, the question is how much. I've seen some high mileage car motors that you could flush a million times and you wouldn't get the build up cleaned out. The only real way to clean them was to take the engine apart. I will try flushing the pan with solvent(engine off) and shot of compressed air back through the hose to dislodge anything that might have gotten stuck in there and see if that helps. The machine is a 1993 and the hour meter was stopped when we got it. Is it likely the flushing will clean out the pan or should I plan of pulling the engine in the near future?