over twenty-three years of using Castrol Lubricants in nearly thirty vehicles and NEVER an oil related failure. I built all my own engines for my MGBs and Big Healeys, I had the opportunity to see the inside of engines I built years prior. They were ALWAYS clean as a whistle and NEVER any sign of sludge buildup. The M Rdstr is my first experience with the synthetic oil (changed it today at 21612 miles...) and I expect it to maintain Castrol's high regard for quality. Randy 99///M Rdstr (current) 01///M Rdstr (less than five days away @ HC:))