Richard J Kinch wrote:

They're all more or less paint. Nothing is going to "penetrate" and
renew the dried-out asphaltic concrete. The only way it could be
"slippery" is if you put so much on that you have a thick enough coating
to produce a flat surface.

Some people just want to believe a mere paint job will extend the life more than
trivially.

Regarding true penetration of the sealer, I agree. However, a painted
vs. an unpainted surface of any kind is generally protected more than
trivially. The purpose of sealcoating in a colder climate, or where
there are seasonal shifts, is to prevent penetration of water into
small cracks where a freeze/thaw cycle causes cracks to expand. If you
can fill those cracks in with sealcoat (a good coat of "paint"), they
won't fill in with water. Sealcoating doesn't "renew" the asphalt in
the sense that it replaces lost oils. The renewal is surface and
cosmetic in nature. It does, however, protect the asphalt. After all,
a good coat of high-solids paint protects the wood on a house. It
doesn't "renew" the wood in any technical way. Its renewal is also
surface and cosmetic.

Here in the Chicago area, roads are constantly being repaved because of
frost heave. This is because water has a fairly unique property among
liquids. Due to the polarity of water molecules, when ice crystals
form, water actually slightly expands and is at its least dense right
about the freezing point. This means that any water which gets into
cracks as a liquid, then freezes is going to push apart the sides of
the cracks, opening them up more. Run through a freeze/thaw cycle a
few times, and you have an ever-expanding crack. As a little
experiment to demonstrate this, you can put a paper cup filled with
water to the brim in the freezer, and come back the next day when it
has frozen. The ice will probably be pushed out over the top, and the
paper cup may actually be torn.