Brakes should be bled (Replacing all the old fluid) with new fluid every 2-4 years, as this stuff absorbs water from the atmosphere which reduces the effectiveness of the brakes to the point where one hard stop will heat up the caliper/fluid to the point of boiling the water and will lock one or more calipers (NOT A GOOD FEELING). Any good silicone DOT 3-4 brand name will work. EXAMPLE:
Valvoline DOT 3 and 4 Synthetic Brake Fluid (32 oz.) 601458: Advance Auto Parts
There is a posting that shows who manufacturers what brand name fluid on this site. If the operations of your brakes is not a factor then think of all the rust that is building up in the system as more and more water gets in there.
DISCLAIMER: yes, people drive cars every day without ever bleeding the brakes system and experience no issues as long as they owned the car. Yes, the fluid is dirty, yes it contains water, yes the system is compromised more and more as time goes on, but they don't see it or feel it so it must not be happening. This is often referred to as the ticking time bomb of deferred maintenance costs.
Process:
Bleed the brakes in the normal fashion RR, LR, RF, LF (All positions are as if you are sitting behind the wheel). I personally would recommend a power bleeder but it can be accomplished with a volunteer who understands basic commands like "Down" - meaning push on pedal until it bottoms out - there this no need to mash the petal, just a firm push will do. "UP" means release and do not touch the brake pedal until you have closed the bleeder screw on the caliper. 9-29 pedal pushes will move most of the old fluid through the system and out the Right rear. The fluid will turn clearer.
The Power method is much better as you are creating pressure at the master CYL with fluid pressure that moves all the junk out of the complete system. Plan on 1-2 hrs or a whole lot less of you have done this before. See online Vids of the process.
CAUTION: MAKE SURE THE MASTER STAYS FULL OF CLEAN NEW FLUID, during the process. Otherwise you run the risk of injecting air into the system and your troubles will magnify.
Oh, and find someone who knows cars unlike my helpful wife who was pushing on the gas pedal while talking on her cell phone and yelling "there is no resistance all all" as I rolled around looking for the complete split in one of the hoses. Note to helper: the brake pedal is the fat one that goes L-R not the skinny one that goes up and down.
