Mobil 1 0w40 is very popular on this forum, but Mobil 1 5w50 is also available to me. My manual calls for 5w50, but as this machine will not be pushed hard, I'm not sure 5w50 is necessary. I believe 0w40 offers greater start-up protection at all temperatures. Perhaps the start-up protection offered by 0w40 exceeds the potential benefits of 5w50. I would appreciate your suggestions.