I've used REV-X. Works very well. I actually have some in the current oil, and it has eliminated the minor stiction issue I was having. I have also been running Chevron Delo 5W-40 Full Synthetic engine oil for several years. That helped also, and it starts much easier in the winter. Between the Delo and the REV-X, I have no sitction issues.
One difference between the REV-X and Hot Shots, is REV-X replaces much less than Hot Shots, does.
REV-X is only 8 ounces and Hot Shots is 64 ounces, for the initial treatment of each. then maintenance is half that amount, 4 oz and 32 oz respectively.....