It depends on the brand of shock, and what type of riding. For hard trails, or tons of jumping, I will run a slightly heavier weight oil than comes standard in the shock. Typically elka's, axis, and TCS call for a 3 or 5 wt oil... In works I like to run a 7wt, since their seal tolerances are a little looser than the other three brands. If you find a place to order the seal heads complete for the shee rear shocks. The place I used to get mine from discontinued them, and now I'm without a source.