I recently bought an 04 MS that has over 24000 miles. Previous owner said he always (since new) used regular dino castrol 10w-40. It runs great and there are no leaks. I would like to take advantage of some syn. oil for smoother shifting, but I"m afraid I'll get leaks from the thinner oil? I know it's not like I'm trying to change over from dino to syn. on a 30 year old bike. I'm either going with mobil 1 high milage syn. or the Shell 5w-40 syn. Any thoughts appreciated. Thanks.