Carl, the endurance gel is great on tires, but if you put that stuff under the hood, you would end up with parts covered in slimey gel and working on the car would become a giant pain. I like the CD2 because when it cures, there is no slick residue left behind, just a black part, but I only use it on the engine bay because it has to cure. I also use the endurance on my wheels, other than the fact that some comes off onto the fenders everytime you put it on, no matter if you try to wipe all the excess off or not....