I read somewhere (source forgotten) that it'* a good idea to put belt dressing onto any new belt to prolong its life, quiet it down, and such.

I've never seen, or even heard of, belt dressing before. Does this apply to cars? If so, it is worth it?

The one time i used it all it did was made my belt squeal and hold moisture..That was just my experience with it on a ribbed belt on my last camaro

EDIT what may work help prolong it is the dressing that you get for windsheild wiper blade lol maybe idk im tired gotta go nite nite

I used it a very long time ago when V belts were used. But I have never used them with the ribbed belts. I see no reason use it.

Belt dressing was used a lot for older v style belts. I remember by Dad using either a bar if soap or ome hairspray to stop sqealing. It worked!

I used belt dressing on the serpentine but it made it squeek and was making it disintegrate little by little

No! Belt dressing is not made for sperentine belt systems. It will do nothing but cause your belt to slip and squeal and will take hours to clean off the belt and pully system. if you just replace the belt after using the dressing, the dressing wil stil be all over the pullys

Brake Fluid is cheaper and will last longer

Your new belts should last you 50K or so miles. No need for dressing.

X3. Modern ribbed serpentine belts/tensioners/systems were designed to make belt/pulley systems work better and not Need any dressings, compounds, solvents. All of which create a mess of some degree and invade the material and shorten lifespan. It your serpentine belt is slipping, it'* worn out. Replace it. Anything else is a waste of money and the belt'* going to fail you likely somewhere you wish it hadn't.

X2

but in a jam if your belt is squealing/slipping a few drops of Brake Fluid is your best friend !! It will get you to the parts store !