I use good ol' plain ATF. Never tried the SF, but have heard good things about it.
In all of my ic engines, I add it on schedule to the fuel regularly and to the oil for a few hours prior to a change.
In a coked-up old engine, it will clean one out in a hurry, too. ---So much so that if used too strongly in the oil, it will cause literal chunks of carbon/tar to come loose in pieces, threatening oil flow, so....
(Quality, synthetic engine oil will actually do the same, so FYI!!)
Anyway, I got on to ATF in the fuel/engine, b/c while still in HS I worked at an FBO, and we retrofitted all the light planes with the kits to run on automobile gasoline. Boss was instructed that if he would always mix some Marvel M Oil (~ATF) into the fuel, that he would have none of the usual buildup/etc prob's with the car gas. We were skeptical to say the least, but followed the tip.
Sure enough, it worked wonders on keeping the internals sparkling clean. (LOTS of detergent in it.)
I use this stuff in my parts-washer, I clean my shop-hands surgically clean with it in seconds, (even into the cuticles), as well as feed it to my engines periodically. Way friendly to delicate parts, and unbelievably effective.
Pine oil (this is ~what B&G sells that works so well, but costs $$$$) will also clean an old engine out marvelously, but kills the oil's lubricity at the same time---as will running an engine ~WFO while spraying a mist of hot water down the intake! LoL