some thoughts from a newbie to this site... (not a newbie to cars)
I've used Slick50 on several cars. Each car was bought new, & we kept them to fairly high mileage:
'86 Jetta; sold it at 146k miles; Slick50 starting about 50k
'89 Saab 900; sold at 220k miles; Slick50 from 35k
'95 GS-R; still going at 111k miles; Slick50 from 16k
Never had trouble clogging the filter. The stuff is fine enough to go thru. None of these have had any trouble with the oil. Or with rings or bearings. When we sold the '89 Saab a couple months ago, the cylinder compression was still really good.

So I never saw any damage, but does it do any good? I have my doubts, & I may not use it in our newer cars. ('98 Accord & '01 Saab)

Synthetic oil...
This is like starting a holy war over on SaabNet.com where I also hang out. Everybody likes it, but many people say that it'll make an older engine start leaking. Others point out that just means your seals were already gone & the dirt was holding them together. There are people over there that switch to synthetic after years of petroleum. YMMV...

I use synthetic on the '01 Saab since its required for the turbo bearings, don't use synth on the others.