Requesting feedback on the use of these products. Do they improve the belt life or should they only be used to quite older belts until replacement. Should they be applied to new belts?
Belt dressing was used on V-belts to locate a noisy belt because there was more than one belt on the engine. So it was used as a diagnostic technique. But since most vehicles now run a single serpintine belt, if the belt squeals you replace the one belt.
Tester
It won’t do anything but glaze the belt once it dries out. Only use it on a very old belt that is so noisy you can’t stand it, and just as a band aid to get you to the auto parts store to get a new belt!