It's handy stuff. I used it in the gas of my last Jeep religiously, it ran better and got better mpg too my guess working as an UCL. I've used it a few times as a crankcase cleaner, it is pretty mild in that regard but it can help. Had a couple vehicles that I got caught with summer oil in the crank when it turned cold, some MMO made a dramatic difference in cold starting until I was able to get it changed out.
Works really well as a gun cleaner too. Crud just melts off with it. I have used it as a gun lube as well, although it will dry out a bit faster than many gun lubes.
Then there's OPE....
Like I said it's handy, and not expensive either.