If you read the manual it calls for the following tranny oil for the 07 WR450 Using Yamalube: Up to 70 degrees 10w-30 50 degree and up 20W- 50 Does not sound like there is alot of overlap. I do not like the idea of the 20W to to engine wear while it is cold and thick. How about just running a high quality 10W-40? This will cover the low temp and high temp. Manual shows 10W-40 in the lower graph but not made by Yamaha. What oil are all you running? I cannot believe that Yamalube is any better any other high quality oil. Any feedback?