This may work
@emichel6888 AGS SIL-Glyde Silicone Lubricant, Tube, 8 oz?
Maybe, but I would not use it without some sort of documentation from the manufacturer stating that it is acceptable for piston seal lubrication with DOT 4 brake fluid. I am not a chemist so take this for what it is worth, but here is what I can see.
The description says:
“Sil-Glyde® Brake Lubricant is a silicone-based brake lubricant recommended for the entire brake assembly, is compatible with plastic and rubber (EPDM & Nitrile) and dampens vibrations between contact points. It is moisture-proof and heat resistant to over 425 degrees F (218 degrees C), which means it won’t burn-off like other brake noise products. Its long-lasting properties provide a noise-free brake installation and easy disassembly. Using AGS brake lubricant is one of the keys to eliminating disc brake squeal and protecting parts from corrosion and rust.”
It does say “the entire brake assembly” however, that typically refers to all external components only. I don’t think we can assume internal components are included in that statement. Looking at a tube of Syl-glide label, it does not say anything about using it internally however, it does say to use on caliper slide pins, seal boots and shoe contact points, but again nothing about piston seals.
It also says it is compatible with EPDM rubber so that is an important one up improvement from the Permatex grease recommended by RB. However, it also says that it is “silicone-based” which would indicate that it is not compatible with Glycol based DOT 4 brake fluids.
Silicon fluids do not mix with brake fluid; however, an argument can be made that the small amount of grease left in the system after rebuild and bleeding should be minimal, and might not be enough to cause concern, but that is pure speculation on my part so…
The old Sil-Glyde msds I found shows it to contain castor oil, polyethylene glycol, and just a bit (7-13%) of some type of silicone/silica component. So perhaps Sil-Glyde is not a true silicone product like the Dow and 3M brake/dielectric greases. However, AGS is vague about the chemical makeup of this grease claiming a “proprietary formula” so only they can truly advise on its compatibility in this application.
Then there is the fact that we have no idea what chemical in that CRC silicone/ceramic grease ate those pricey BR silicone dust boots. So how do we know this Sil Glyde does not have the same chemical? Since we are not entirely sure what is in it, or what interacted with those high temp dust boots.
So sure, you can try it, and it might be fine, but I have to ask why? When we already have a grease specifically designed for this application that has been in use and proven for decades, and in both street and race applications. It is 100% compatible with virtually all rubber, silicone, and DOT 4 brake fluid. Why would you bother to take a chance on something that may or may not have some unforeseen chemical interaction?
Like I said I have tested it at over 600 degrees and plenty of folks use it in race applications and swear by it, so what exactly is it that makes you feel like you have to find something different?
Just use Red Rubber grease:
https://www.ebay.com/itm/2-oz-100-P...863421&hash=item3f6c313bcd:g:5Y4AAOSwYIxX8Ev8
Or if you really want to try something different, there is the special formulated lithium based grease that VAG specifies part # G052150A2
https://www.ebay.com/itm/362498323200 I can’t find any specifications on it, but clearly it is compatible with the piston seals and DOT 4 brake fluid. Although we have no idea if it is compatible with those silicone dust seals, but personally, I would use that over some random brake caliper grease.