That reminded me of a procedure that my brothers liked to suggest about 30 years ago. We called it “blowing out the carbon”. The situation was a car had been driven gently for 5 years. The theory is that soot was building up in the cylinder, valves or exhaust manifold, etc. The procedure was to take the girlfriend’s mom’s car out on a country road and drive it at 80+ mph for 15 minutes or more (more if you knew where the local police squad was so you could go where he wasn’t). The discussion usually ended with the story of how the girlfriend’s father was unhappy with whatever the boyfriend had done to the engine and wanted him to change it back.
I’ve heard it referred to as a “ten cent tune up”. All this reminds me of a '77 Suzuki GT380 MC I used to have. It was a 2-stroke; which meant it normally burned oil. I’d cruise down to the Jersey Shore occasionally during summer, high speed cruising the whole way. For about a week afterwards it would run like a top, so maybe there’s something to this.
Alternatively know as an Italian tune up, my diesels also like it occasionally.
Yes the old Italian tune-up. It is usually recommended by a teenage boy who wants to see what pops car does. After all these years various theories have been created by those boys and some of them are in general use today. In a few occasions they may even work.
My mother-in-law used a can of Karbout twice a year when she had a carbureted car. It softens the build-up and then her son would drive it briskly on the freeway for 30 miles or so. It worked great on her Buick, Comet, and Marquis. Her present car has fuel injection, and there is considerably less buildup. But you can still buy a version of Karbout which will not harm the engine sensors. Still need that fast drive on the freeway.