# Brake Fluid: adding brake fluid: OK to use DOT 3?



## Kel (Mar 29, 2003)

Book says use DOT 4. 
1- Any damage or problem is you use DOT 3?
2--Does it have to be Synthatetic? What happens if it is not?


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## Fast Bob (Jun 4, 2004)

Kel said:


> Book says use DOT 4.
> 1- Any damage or problem is you use DOT 3?
> 2--Does it have to be Synthatetic? What happens if it is not?


Don`t be stupid....you have to buy it *anyway*....(NEVER use fluid from a previously-opened can)....just buy the DOT 4

"Synthatetic"??? (never heard of it


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## mechanicalmagic (Dec 26, 2008)

Kel said:


> Book says use DOT 4.
> 1- Any damage or problem is you use DOT 3?
> 2--Does it have to be Synthatetic? What happens if it is not?


1. DOT 3 is a hydraulic fluid that absorbs water. That water can settle in the calipers, and if they are made of steel, they will rust. This was common in the "old days". Water in the brake fluid also boils at a MUCH lower temperature, so it must be changed often. Depending on the rubber compound, the seals in the calipers MAY swell or shrink.

2. All DOT 4 is Synthetic, or Silicone fluid.

If you drive like a little old lady, then save $5. BUT it will cost you in the long run, and maybe right away.

DJ


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## DSXMachina (Dec 20, 2007)

Here are the facts; DOT 3 and DOT 4 ARE MIXABLE! The difference is that DOT 3 has a lower wet boiling point. DOT 5 (NOT DOT 4) is synthetic and cannot be mixed with 2-3-4. 
You want to flush out your brake system and install pure DOT 4 in your BMW to take advantage of its higher resistance to boiling due to moisture absorption. In the meantime you have NOT harmed your brake system in any way. You just don't want to go racing with the car right now.
Take the above info to the bank.


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## DSXMachina (Dec 20, 2007)

Here is some information you may wish to read. I cut and pasted it from the original which was by Dave Zeckhausen.
*Thanks to Dave Zeckhausen : 
Lets look at what the DOT ratings mean. The table below shows the MINIMUM wet and dry boiling points for DOT 2, 3, 4, and 5 brake fluid in degrees fahrenheit. 
___________________ DOT 2_____ DOT 3_____ DOT 4_____ DOT 5 
Dry Boiling point ______374 _____ 401_____ 446_____ 500 
Wet boiling point_______ 284_____ 311_____ 356

The DOT 2 spec is for drum brakes and is obsolete. If you have any DOT 2 in your garage, throw it away! DOT 5 is for silicone brake fluid. Silicone brake fluid (DOT 5) should be avoided because it is not compatible with regular brake fluid, it is hard to pour without introducing bubbles and thus results in soft pedal feel, and moisture still gets into your system and will pool in low areas like your calipers and encourage rapid corrosion. STAY AWAY!

That leaves DOT 3 and DOT 4 fluids. These fluids are compatible with each other and may be interchanged or mixed with no ill effects.

Let's look at some popular brake fluids and their boiling points:

Castrol LMA is very good at rejecting moisture and may be kept in your brake system for a couple years. The LMA stands for "Low Moisture Activity". This is the minimum quality stuff that I would use in my Impala. It comes in plastic containers which do not have a long shelf life. Don't buy lots of this stuff at a time because moisture can make its way through the plastic containers.

Ford Heavy Duty DOT 3 is VERY inexpensive and is popular among racers because of its excellent dry boiling point. It absorbs moisture quickly, but the racers don't care since they change their fluid frequently. Comes in metal cans so it may be stored. I would not use this in my Impala for the street.

ATE Super Blue Racing and ATE TYP 200 are the same brake fluid in two different colors (blue and amber, respectively). BMW recommends this brake fluid for their street cars because it, like Castrol LMA, absorbs moisture very slowly. The advantage over LMA is that ATE has a much better wet boiling point. You can put this stuff in your car and forget about it for a long time. An excellent choice for a weekend track car which also sees regular street duty. Comes in metal cans. This is what I use in all my street cars.

Motul Racing 600 is a very exotic and expensive synthetic fluid with high wet and dry boiling points. I use this exclusively in my race cars. Too expensive for the street and requires frequent changing due to its hygroscopic nature. Sold in plastic bottles. It is not suitable for the street because it absorbs moisture quickly.

Castrol SRF is a hyper-exotic and hyper-expensive brake fluid that is generally used by wealthy Porsche owners at track events. I've seen prices of $78 per liter for this stuff. Sold in metal cans. I can't afford this stuff!

Performance Friction High Performance DOT 3 has a good dry boiling point but a crummy wet boiling point. It comes in metal cans which is good for shelf life and sells for $7.87 per 16 ounce container. If you are even considering this fluid, I would go with the cheaper Ford Heavy Duty DOT 3. In either case, change this fluid frequently due to the poor wet boiling point. *


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## kevalent (Jun 7, 2007)

Great find on the info DSX. The only thing I have to add it that a few years ago they came out with DOT5.1 which is not silicone and is compatible with DOT3/4 fluids (make sure it has the '.1'). I use this in my motorcycle that originally came with DOT4 and it works great...just a little more expensive but the boiling points are a fair bit higher that DOT4 so I can justify the extra couple bucks for the bike. For the car I would prob. just stick with DOT4 unless you track it in which case the 5.1 might be a worthwhile upgrade.


DOT 5.1 
DRY BP -> 270°C (518°F) 
WET BP -> 191°C (375°F)


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## ROCKYTOP2 (Jun 14, 2009)

Can any of your guys show me where to add the dang brake and power steering fluid ?? My manual does not say and neither does a search on threads for 2007 550i... Im low on both! Thanks in advance...


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## ECSTuning (Feb 25, 2009)

It's important to change your brake fluid every 1-2 years.

We offer you a large selection of fluid to meet your specific automotive needs specifically for your BMW.

*Click HERE for more information.*


Please let us know if you have any questions! Feel free to shoot me a PM or email.

Best,
Joe


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## Killjoy (May 13, 2009)

ROCKYTOP2 said:


> Can any of your guys show me where to add the dang brake and power steering fluid ?? My manual does not say and neither does a search on threads for 2007 550i... Im low on both! Thanks in advance...


try posting in the e60 sub forum, and you will get a more accurate answer there.


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## mitsuo39 (Jun 7, 2021)

ROCKYTOP2 said:


> Can any of your guys show me where to add the dang brake and power steering fluid ?? My manual does not say and neither does a search on threads for 2007 550i... Im low on both! Thanks in advance...


Its drivers side under the filter. Yes oind of a stupid place to put it!


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