I put Lucas oil stabilizer in my old truck's crankcase over two weeks ago. The lifters were making a clicking noise after the valve cover had been replaced. I used part of the contents initially. The clicking noise still continued for some time after the application. I added the remaining contents on Monday night after coming home from work, Yesterday, the loud clicking noise dropped down substantially. I was expecting the product to work in roughly 5 days or less, not 2 weeks. Perhaps it takes a bit of time for the stabilizer to thoroughly work through the engine to complete the task. It was a lesson in patience. My 1991 Mighty Max truck has over 250,000 miles on it and I want to keep it until it "drops dead". Have a blessed day and keep up the good work. Respectfully, Alan Strong