Chris If your an x- moto cross guy then you know of belray oils. Belray gear saver 85 wt will stand up to the most abuse, or go with the 80 wt. for less drag on the motor, the motul trans oil is excellent chioce also. If you you can afford to change it after every race weekend that is best, but i would not go more than 3 race weekends. Then in the off season have your trans polished, it will shift like butter and last longer, you can do it your self but it takes about a good 8 hrs to do it right.