DOT 5 Brake Fluid?

[Guest tony78_280z]

Somebody said something about a DOT 5 brake fluid. I can't find the post anymore. Is this a rumor?

 

Where do I find it? Walmart don't carry it.

 

Does it work on all systems?

 

Does it realy absorb water?

 

Is it realy safe on paint jobs?

 

I'm doing brake work this weekend and am thinking about flushing and replacing with this mysthical substance.

 

Jeesh I probably sound like an idiot talking about something that doesn't exist.

 

Thanks

[mark]

Dot 5 is silicon based fulid. Don't use it. It is not compatable with other fluids and from what I hear it loves to soak up moisture. Use a good quality dot 4 brake fluid. If you are doing track events look for something like motul, high wet and dry boiling points, if this is just a street driven car, vavoline makes a good all around fluid. I've used it for track events with reasonable results but now use motul for the track. Mark

[johnc]

EDIT: What Afshin says below...

[Afshin]

Here is a very long summary about brake fluid from my files that I posted a long time ago:

 

DOT 3,4 and 5.1 fluid are all glycol based and generally compatible. However one may offset the benefit of the better fluid if mixing it with lower grade, so it’s always better to flush the whole system with the newer fluid. Also some are more different than others despite the same DOT rating, ie synthetic, different viscosities and different amount of hygroscopic (water absorbing) properties causing them to absorb brake system moisture, and over time the boiling point is gradually reduced.

 

The Dry Boiling Point is the temperature at which a brake fluid will boil when new in its non-contaminated state and the wet boiling Point is the temperature a brake fluid will boil after it has been fully saturated with moisture. The requirement for wet boiling point minimum is 284F for DOT 3, 311F for DOT 4 and 356F for DOT 5.1. These numbers are the minimum and many of the better brands far exceed the minimum requirement (e.g. castrol SRF has wet boiling of 518F, dry boiling of 590F).

 

Difference between Dot 4 and 5.1:

DOT 5.1, albeit confusing in designation, is effectively a lighter viscosity synthetic poly glycol fluid with DOT 4 performance parameters. It was developed for use in mechanical ABS systems that require a higher cyclic rate to better deal with pulsations. It is not a “higher “performing fluid.

 

DOT 5 is a silicone based synthetic fluid originally designed for use in military and government vehicles where regular maintenance could be problematic. It is non corrosive and is marketed as a “lifetime†fluid often used to preserve brake systems in antique vehicles and those that sit for long periods of time between use. It was never intended for high performance application. DOT 5 fluid is not hygroscopic, so it does not absorb water and may be useful where water absorption is a problem as one of the reason for its development (military equipment and tropical environment..). However and perhaps ironically this brings up another serious concern as moisture enters the system (can not be prevented), it is not absorbed by the fluid, and can result in moisture collecting in the calipers which can very easily boil causing vapor lock and system failure or can cause corrosion where the water collect (it has to collect somewhere since it is not absorbed). DOT 5 fluid is now most used/best suited for show car applications where its anti-corrosion and paint friendly characteristics (does nor ruin paint) are important. DOT 5 is not compatible and can not be mixed with other fluids since it can result in slugging.

I think previously some race teams used to use DOT 5 it because of it’s higher boiling point, however the new poly-glycol synthetic fluid have the same or even better boiling point along with better pedal feel (dot 5 is more compressible and has spongier pedal feel) so DOT 5 has fallen out of favor.

 

Personal recommendations:

DOT 3 is outdated and not suited for aggressively driven cars, dot 5 is problematic and should be avoided. DOT 5.1 is good and best suited for ABS systems which leave us with dot 4.

 

 

-Castrol SRF. amazing fluid, (wet/dry 518/590F) very low hygroscopic affinity (does not absorb much water) and the highest boiling points, and the most expensive by far (actually it is a silicon ester not a glycol based fluid, but it is not the same as the dot 5 plain silicon which can't be contaminated with glycol based fluid)

-Castrol LMA. (LMA=low moisture affinity) cheap, available at most stores, not race fluid but very good as low maintenance and high performing fluid and is actually suitable for most aggressive street applications and can still handle occasional track days with vented rotors.. (wet/dry boiling 325/490)

-Motul 600 one of the best race fluid(based on wet/dry boiling point of 421/585F) along with Neo (identical) but is also very well priced, can be used for daily street/track cars. Does absorb more water (more, but not extremely hygroscopic like most race fluids which need to be changed very very frequently).Great choice if car goes to track often, if you don't leave fluid in over 8-12 months and if live in a dryer climate.

-Ate type 200 also known as super blue and super gold (wet/dry of 392/536F). Outstanding fluid good for race and street, can last for two years (not racing off course). This fluid is possibly the best for aggressive street as well as track use type of car/driver. It is also cheap, best found online, has a wet boiling point of 100F greater than the

Ford HD or AP 550 fluids (AP 5.1 matches the Ate but is much more expensive) and works well on the track for me. Also with the different colors for this fluid (blue and gold), when flushing your system you can tell when the new fluid comes in by the color.

 

One last point, while technically the different non DOT 5 fluids are all compatible, it is not advisable to mix them since people have reported poor performance, spongy pedal feels and so on when doing so. It is best to flush the system when upgrading to a better and new fluid.

[Guest tony78_280z]

Wonderful Information... Such vast knowledge... Outstandingly technical... Ok that is far too technical. I'm confused. With my specs below and driven as a daily driver with very little racing (other than the coffee can muffler having bass music pounding ass at the stoplight next to me) what type and brand of break fluid do you suggest. Tell me, and I'll take your word for it, and buy it tomarrow.

 

Thanks

[JMortensen]

ATE Super Blue