I agree a lot of them are "snake oil" I have heard that Slick50 used over long periods makes it a tough to deglaze a cylinder when the time comes as it soaked into the metal deep enough to make deglazing tough. I personally swear by Duralube and use it in ALL my engines including lawnmower etc. I have 5 acres of lawn to maintain and my lawnmower - used for edging - is 20 years old -on it's fifth set of wheels and still the original aluminum block B&S engine that does not burn oil and still has great compression. What really convinced me is my daughter's 89VW diesel. Three years ago in August when she got it - I put in duralube. The valve cover gasket was leaking but I didn't have time to change it so I told her to check her oil every week. As a typical 17 year old girl - she FORGOT. At christmas that year - I had to change a glow plug for her. When I test drove it, there was a loud clunking coming from the engine. It had just started as she never head it. The engine rocked and clunked merilessly. When I checked the oil - the dipstick was dry. When I drained the pan I got 1/2 quart out. I thought the worst. When I disassembled the engine I was shocked to find the mains and shells were NOT EVEN WORN -no marks whatsoever! The rings had a slight razor edge to them - but nothing serious. The clunking was a stuck hydaulic lifter from lack of lubrication. Since it was apart I replaced all lifters, lapped the valves, and put in new mains, shells, rings etc. This engine still runs like new 2 years and 50,000 miles later. What should have been a throw away core I believe was saved by Duralube. Has anyone had bad luck with Duralube??