Wilson, is Motul oil designed for the S&S V twin? I believe "V Twin oil" as S&S suggests has ZDDP (Zinc) in it for the anti wear properties. Please correct me if I'm wrong. I always use Mobile One V twin oil--it says on the label for V twins
For use in the south of France where the ambient temperatures can sometimes be over 40º, both Raphy and I wanted the extra protection of a 20W60 oil over a 20W50. When my car was working, I measured the oil temperature after a long hard run. It was around 110º. Whereas this is a problem for the oil lines that Morgan fit, which are only rated to 100º, it is fine for the oil, rated to 165º. I had a very helpful discussion with Motul's competition department. They felt that the 20W60 300V Le Mans oil was ideal for an air cooled engine, being operated in high ambient temperatures.
Wilson
PS During the rebuild, I have had an oil temperature gauge added, so I will keep a close eye on the oil temperature. If I feel it is getting on the high side, I will add an oil cooler to the return to the oil tank side of the system. The problem is a suitable location for the cooler. Down in front of the engine, is too vulnerable to parking idiots and in the grille gets no cool air. I think mounted on the side just behind the wishbones might be the best place.
