Any preference on Dot 3 manufacturers? What about synthetic vs non-synthetic?

DOT 5, Royal Purple

But the label on the brake fluid fill canister says 'Use only DOT 3' brake fluid. Will a Barth Gremlin attack me if I do otherwise? Seriously, there have been comments about seals etc adversely affected by anything other than DOT 3
??

Good question, Jim. I've seen several times that people had reservations about changing from Dot 3 to Dot 5 fluid. Dot 5 has higher boil pts but I have read about seal problems, too. I'm still using Dot 3.

Frankly, the whole brake fluid thing is new to me. Living in Michigan, I have almost never seen brake fluid go bad. There are LOTS of vehicles around here with factory original fluid. Since I drive slow, don't tailgate, don't tow trailers much and don't go down mountain hills I rarely have brake heat problems anyway.

(Same with airplanes, PO of my plane put brake pads on every 2-3 years... I go 10. My A&P says, "do you ever USE your brakes?" It's all about planning ahead, energy management and coasting.)

OTH, there is no question that climate has an effect. Higher temps and esp high humidity will turn brake fluid to dark jello. When my Dad lived on the gulf in Texas he had plenty of brake fluid issues.

Any experts to weigh in here?

quote:

Originally posted by Steve VW:


Living in Michigan, I have almost never seen brake fluid go bad. There are LOTS of vehicles around here with factory original fluid. Since I drive slow, don't tailgate, don't tow trailers much and don't go down mountain hills I rarely have brake heat problems anyway.

Brake heat problems are one good reason to change fluid yearly.

Another reason is to get rid of moisture build up that can cause rust and other corrosion. A good brake shop has a moisture tester. Or you can buy test strips.

Messing about with old cars since the '50s, I have seen a LOT of rust pits in brake cylinders, calipers and lines. Had to scrap a lot of gear that would have been hone-able without the rust pits.

Also have had rust flakes and moisture crud mess up a brake cup now and then. This can drive you crazy, as the flakes will now and then allow a little air to get in the cylinder on the return stroke. Bleeding, of course, did not help.

The only time I had brake fluid heat problems was in stop and go traffic on a jammed El Lay freeway. Our brakes slowly went away. I used low gear, trailer brakes, and extreme caution to get off the freeway. By then the brakes had come back. I believe the fluid was two years old at that time, and was a good brand. Prestone, I think. I do not drive in the rain, so the fluid just picked up moisture from our damp coastal air.

Speed Bleeders make brake bleeding so quick and easy that it is a very cheap safety and anti-corrosion precaution. Getting to the reservoir is more work than the bleeding itself.

Someday, I may cobble up a remote reservoir.

Dot 3, Dot 4, or Dot 5.1 are all types that can be used on the air/hydraulic system. Dot 5.1 has the highest boiling temp. They are all hygroscopic so they will absorb water as time goes by and should be changed or flushed on a regular Basis.

These are polyglycol ether based fluids

Straight Dot 5 is silicone based and does not absorb water but water in the system will turn to steam and then air over time to degrade the break performance. Dot 5 fluids compress more than Dot 3, 4, 5.1, so the brake peddle will feel more spongy or soft.

You can not mix Dot 3,4,5.1 with Dot 5 fluids. Full and complete flushing when changing to silicone based Dot 5.

I have used Dot 4 since 2006 and have had no issues. I flush every year, but I put on in excess of 20K miles each year.

HTH