There was a big "snake oil" test of coatings and oil additives in the leading german vintage car magacin a while ago.
The did a test with several identical rebuild vintage (Ford - there goes the 4 letter word

) engines on teststands and simulated 65 000 miles of normal driving, cold starting and any kind of abuse you can think of.
The coatings performed pretty good for a while, but they wear down after max. 20 000 miles.
There where only two products that showed significant milage/performance plus and protection against wear.
the winner was
Mathy Here in southern Germany we used this stuff since years. It is a well known "liqid speed equipment" for performance engines and hevay duty stuff.
It also has an intresting history:
It was invented by Otto Mathé, the celebrated sports hero in Austria and Southern Germany, he was a living legend, being one of the most successful racers before and after the war.
In 1934, during a dirt-track race, Otto Mathé crashed his motor cycle, leaving his right arm lame for the rest of his life. But a fellow like Otto Mathé, called the "Tyrolian Daredevil" could not easily be stopped from racing. First on a sidecar outfit, altered to his demands, later on a great number of sports and racing cars. Wherever Otto Mathé was at the start line in one of his cars like CISITALIA, FIAT Ballila, Lancia Aprilia, Porsche 356 or even in one of his home-made cars (one of them he used to call the "Tin Can"), in most cases the winner was Otto Mathé. In 1952 he took victory in 20 (!) road races. In 1953 he was third on the famous NÜRBURGRING race course behind Pininfarina and Juan Manuel Fangio. It was only the second Grand Prix Mathé competed in.
His numereous performances (and wins of course) at speedway events and ice races have become legends. Especially so, when he raced on the ice surface of the Zeller See (Austria). The steel spikes of appr. 10 mm length his racer (called "Rags Afly") was equipped with gave a most spectacular sight when he went round corners!
He was also an graduated engineer and took special interest in dismantling engines, making improvements, putting them together again and making experiments. Just before he died in 1995, he worked on methods to considerably reduce fuel consumption. He was convinced that the lubricating abilities of motor oils were overestimated for many years, so he developed a formula for oil additives which was unique in his time and still is. Even in the early sixties Mathé was able to race his Porsche 356 (1500 cc) for more than 100 000 km without oil change, using his own additives. Of course regular change of the oil filter and replenishment of the oil consumed was executed.
Oils on sale consist of short molecule chains. MATHY will connect the oil molecules to nearly endless chains, thus multiplying their tensile strength. The result is a lubricating film that is close to indestructible and with the greatest reliability adheres to metal engine parts.
Frank