Seals deteriorate and oil leaks occur and to address this problem, Forte has developed a Seal Conditioner to restore seals' properties to protect engines, manual transmissions and final drive differentials. A major cause of oil burning and smoking is down to the valve stem seams hardening and shrinking, resulting in oil seeping past the seals into combustion chambers. Forte's Seal Conditioner can be added to all conventional petrol-based crankcase and gear oils.