Notice that through the years there has been dozens of those gimmick addatives. Where are they now? Gone - many because of lawsuits.
I bought some Slick 50 just to see what it's like. It is slippery! I put it in an oiler can - good for garage door hinges, axles on the welder etc. It seems to dry out if you use it outside. I'm not so sure about using it an engine - probably good for bearings and cam, but I'd worry about the rings not sealing - too slick!
Never in a trans, it may be OK in a diff, but plain old 90 wt lasts forever.
I am a believer in STP - I saw some amazing things it's done, but it has to be changed frequently, else it turns to a plastic-like gum. STP was originally designed for cranes - the long tube telescopic extension booms. They needed something that would stay, not run off, and work in hot weather - like Saudi Arabia.
Chevron Chemical Labs developed it for that - my Dad was an engineer there. It was never intended to put in an engine. Studebaker Corp bought the patents, tried it in engines, then Andy promoted it.
I really like 50% STP and 50% 30 wt for engine assembly. But for sure not for break-in. Good old fashioned Dino oil for that - no gimmicks.
Back to the trans and why the correct oil -
Here's a picture of a broken synchro ring - the result of forcing it into gear when it hasn't brought the gears up to speed. Typical of using the wrong lube. When it's too slick it doesn't want to go into gear easily. If you force it in, the blocking ring can break. Complete teardown is required to fix it. Scroll down a little on the site.
THIS IS NOT MY WRITE UP. I simply saved this for other people so DON'T contact me about the tools
Pictures of the fragile brass blocking rings - at the top of the site. Look close and you can see the taper - inside the taper are fine little grooves to help squeegee the oil off when shifting.
Honda Acura Integra GSR Type R Differential Bearing
Here's how a manual trans works -- none of these pictures are of Jeep transmissions, but they all are very similar - they all use the synchros - there's only slight differences in dimensions.
The syncho system is shown very nicely in this article. Note the taper on the gear, note the internal taper on the blocking ring - those matching tapers pressed together act as a clutch to bring the gear up to speed so it slips into gear easily.
How a Transmission Works
It's a very informative read.