California-based Lucas Oil Products is one of the best-known specialty oil manufacturers in the U.S. In addition to a proven line of racing and gear oils, Lucas has a full line of motorcycle products, including chain lube, octane booster, primary oil and synthetic fork oil. We used Lucas’ 10w High Performance Synthetic Fork Oil in our Norton fork upgrade, as it’s formulated to prevent foaming, a common problem in damping-rod forks, and prevents seals from hardening. $6.39/16oz bottle at Dennis Kirk. More info: Lucas Oil