If brake fluid has a high affinity for moisture/water (Hygroscopic) why not use light motor oil or hydraulic fluid instead of brake fluid? Hydraulic floor jacks and bottle jacks use hydraulic fluid, and the brakes are a hydraulic system...So...???

 

Brake fluid needs to have relatively consistent viscosity across a wide temperature range. Brakes need to function, including sealing against the rubber elements of master cylinders, caliper pistons, and wheel cylinder, from -55°F to over 300°F, and DOT4 fluid is rated to nearly 450°F. Wheel cylinders and calipers can get really hot under heavy and repeated braking, and that can cook most oils or boil anything containing water. The viscosity index of most hydraulic oils would be all over the map across those ranges, potentially making brakes almost inoperable at low temperatures and beginning to char at high temperatures.

If you are concerned about moisture, the old brake fluid can be flushed and replaced with fresh glycol (DOT3/DOT4) or you could investigate the option for using DOT5 which has no affinity for water. Just be sure all your system materials are compatible - Many are not.

 

DOT 5?? I've never heard of it until now...THX...Joe I purchased my '85 camaro in '99, and the brake fluid is at least 24yrs old, so I guess it's due for a flush and refill. LOL
I think the left front caliper is frozen, because the last time I drove it, the car pulled to the right when I applied the brakes...I purchased new front calipers from Rock Auto, but I should have gone with Wilwood or Brembo...Is DOT 5 as corrosive as DOT3, 4???

 

My '86 has had a front caliper drag due to an internally deteriorating brake hose. That was a good excuse to flush all its fluid and bleed everything, but that was already 15 years ago.

There is nothing wrong with a Morraine caliper when in good condition. With the right friction material it can stop as well as most aftermarket four-piston non-floaters. If you can lock up a wheel under heavy braking, what more does anyone need?

DOT 3 is not, by itself, corrosive. The problems usually start when it collects moisture, and the water becomes the damaging component.

 

Make sure you do some research in regards to DOT 5 before you try messing with it. There is DOT 5 and DOT 5.1. DOT 5 is silicon based and requires a completely clean and empty brake system and may damage brake components (like o-rings and seals) not designed for it. DOT 5 was designed to be used in applications were moisture is present and the brake system sits for a long time like military vehicles sitting in a depot for years at a time. It has a high boiling point, but is more compressible than traditional brake fluid so pedal feel will not be as good.

5.1 is like regular glycol brake fluid and will still absorb moisture like dot 3&4 will, it just has a higher boiling point than earlier fluids.