I have done a bit of reading on both these ideas, and I am confused. The UCL (whatever the form TCW3, MMO etc) lubricates all the upper cylinder components, fuel pump what have you. Then you have the fuel system cleaner (whatever the form, STP, Amsoil Redline etc). The only problem I have is they seem to cancel each other out. You take the UCL and you lightly coat parts of the system, you take the system cleaner and it cleans the varnish and any oil based residues. So which is better for the car, to be all lubed up, or squeaky clean?...or both...or neither??