I spent a year hanging around a dusty old airport with a bunch of grey hairs. One notable had his flying license since 1921, flew 29's in WW2, was a captain for United, retired, and then starting flying unlimited pylon racers out at the Reno air races. He held several degrees including engineering and chemistry, and yet he taught guys to fly in an old Piper Colt and was still teaching and flying his racer last I heard. The owner of the airport was rebuilding aircraft engines before I was born, and knew more about engines and physics and metallurgy than almost anyone ive met.
Everywhere I turned were these old guys who dressed and acted more like farmers than anyone else, but when they spoke and told stories, you would think you were among the astronauts. They were without a doubt, the smartest men ive ever hung around.
And virtually every one of them used MMO in the crankcase. They showed me airplanes with engines older than me ( I was 38 at the time) which had never been apart, several of which had exceeded their TBO more than twice over. I still recall a 57 172 that was 39 years old and never apart except for one jug (I read the log book), and still posting good compression at over 4000 hours since new. That engine has a TBO of only 1800 hours, and anyone who knows 145 HP Continentals knows they have a hard time even going that far and usually need a top overhaul around midway.
And no one really knows to this day exactly whats in it. All I know is that some years back I ran two quarts of it through an exotic sports car engine to clean it out before tearing it down and washing all the parts in solvent. Even three years later I could pick up parts from that engine and feel a fine silky wax like film, and smell MMO.
Let me say this though. I have personally taken apart as many as 3000 to 4000 engines over my years, maybe more I dont know. I have seen a lot of carnage, not just automotive and racing, but marine engines, aircraft, and heavy diesels etc.. I've seen engines that were sludged up and no longer ran with less than 1000 hours on them, or less than 40,000 miles. At the other end ive seen Mercedes diesels with over 800,000 miles that were still running strong which had never been apart, and other diesels with amazing distances and times on them. And many of those that went the distance had owners who swore by MMO. In all fairness though, those owners also prescribed to 3000 mile or 25 hour oil changes with top name brand oils of higher viscosity.
So y'all can call it snake oil, but there are a lot of really smart people out there that have a long, long history with it that would argue with you. And going back to the airport again, I knew of no one who added it to their fuel. In fact the FAA has vehemently warned against adding it to fuel in aircraft, for safety reasons.
And what do I do? I am in the middle. I often add some before an oil change, maybe a week before, because I know it is highly detergent. I have put it into engines that smoked, missed, or had ticky lifters, and ive seen it fix a great many of them. It can unstick rings and valves and can get ticky lifters working again better than anything I know of.
