750002 Recharged High Mileage Engine Treatment, 15-Ounce

There are a LOT of additives out there, and I wouldn’t put ANY of them in my car’s engine unless/until I’ve figured out exactly how they’re supposed to work, and then decided whether the “pros” of using them (e.g., scientifically measurable benefits) outweigh the “cons” (e.g., added expense/hassle, no measurable performance improvement, potential hazards of use).I’ve got a 2001 Suburban with over 215,000 miles on it. I’ve added Prolong treatment to the transmission fluid, and can’t say with any certainty whether it helped, but I CAN say the original tran is still shifting smoothly/working great after 215k miles. I’ve added lots of different cleaning treatments to the fuel system, all with varying degrees of effectiveness, but am currently using Sea Foam on that system, and I love it … always a near-instant improvement in pick-up/performance that lasts at least a month. Up to now, I’ve never used any additives in the main oil system, except an occasional sludge treatment, applied by Jiffy Lube or other oil service pro.I decided to try Slick 50 after experiencing, among other things, longer and longer periods of valve lifter noise at cold start up. It had gotten to the point where I was hearing the lifters clacking for up to a full minute after start up. I’d been told a number of times over the years, by different mechanics/friends, that most of the “normal” friction damage that happens to valves, lifters and cylinder walls occurs at startup of the engine, e.g., when most of the oil that protects these parts has settled to the bottom of the engine, and has not yet been re-circulated to fully coat/lubricate them.As I understand it, what this stuff does is add a “super lubricant” to your regular oil (compatible with both conventional and synthetic oils), so that when the oil passes over all these parts, the molecules of the additive stick to the part surfaces, and don’t “settle” with the rest of the oil when the engine is turned off. Thus, the parts are ALWAYS coated with a “base” lubricant, that is then continually replenished by the normal circulation of your regular oil through the engine.I emptied out my old oil, put in the Slick 50, then added 5 clean quarts of a high quality synthetic (Pennzoil 5W-30). That put an end to all lifter noise, almost immediately. The 5.3L Vortec engine in this car has always run very smoothly when everything is in good working order, but it became even smoother/quieter when I added Slick 50 to the oil. I literally cannot hear the engine running from inside the car … I have to look at the gauges to make sure it’s running.I probably should have started using an additive like this long before now, but I’ve always been a stickler about following OE recommendations whenever possible, and Chevy’s recommendation for this car was, e.g., all you need is normal oil changes at their recommended intervals … no additives. However, that recommendation was probably valid for the first 100,000 miles or so. Once you’ve kept the car going FAR beyond the OE’s entire maintenance calendar, you’re kind of on your own, and this stuff (their “recharged” formula) is specifically designed to give a little help to engine components that already have some wear on them.There are a lot of additives I still wouldn’t touch with a ten-foot pole, but I’m now satisfied that Slick 50 isn’t one of those. This product has been around since the 1970’s; it works exactly as advertised, and so far, I’m very happy with the results, and consider this product a great performance enhancer/protector for older engines, well worth its modest cost. Five stars.