Not sure if it is available in the US, but I use Molykote 4500 G. It is not based on oil/grease, as some of these greases solidify (crosslink) to form a sort of glue; the same that happens with old fat; which won't even dissolve in soap anymore then.
Molykote is suitable for plastics, rubbers, alu, steel and all their mixes.
These new types of greases are usually white and use of Teflon (PTFE)
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MOLYKOTE® G-4500 FM Multi-Purpose Synthetic Grease
Aluminum-complex-thickened, uses white solids and PTFE as solid lubricants. Also, H1-certified through NSF for incidental food contact.www.dupont.com
It's about the only grease I use in my garage, and professionally.
going back to your problem, if your windows are running difficult, it is likely due to old grease that is gumming up.
I've just removed my window tracks, and the system is actually quite robustly engineered (It uses a spring loaded bearing sled) and it has the ability to run really smooth.
here are some pics of the right door that i just removed from my car. Just adding some addition lube on top of the gummed grease woulnd't have made any difference; the spring loaded wheel bearing sled was completely solidly gummed up. It acted as a sled, with all 4 bearings being jammed.
Also the track was full of gum, in some places up to 10 mm think (close to half an inch).
Herewith some pics to show the dillemma:
Gummed up & locked bearings:
View attachment 175312
View attachment 175313
Cleaned by hand and ultrasonic bath
View attachment 175315
and lubed with Molykote
View attachment 175314
same done with the vent window mechanism;
View attachment 175316
and funny enough, when you turn it back and forth, it starts to run more smooth with every turn, as the lube starts spreading and forcing itself through small openings., even pushing old the older yellow grease in front of the new grease.
View attachment 175317
there it is , yesTaken out to clean separately.
Sounds Tasty! Just wondering, must you remove the whole window assembly to adequately clean and lube this area? I don't want to open a can of worms and break or lose anything?Ok, didn't expect that! But I did use it in my coffee machine!
....
I'll have a look tomorrow or this weekend to see if perhaps you can remove only the bearing block and clean the rails in-situ.
I think the bearing block slides out the top, but not sure if it will be able to do so while still inside the door.