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Discussion Starter · #1 ·
I noticed on the brake fluid thing in our cars that it says to use either Dot 3 or Dot 4 brake fluid a while back when I needed to add some. What is the difference between the two or which one should I use? Thanks you guys.
 

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boiling point.
DOT3 < DOT4 < DOT5.1(Can be used on all DOT3 & DOT4 systems)
 
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Discussion Starter · #3 ·
Which is the best, and is there any disadvantages to using the Dot 5.1 if it can work in our master cylinders and has the higher boiling point :).

Does it change the feeling of the pedal, etc.?
 

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DOT 5.0 is silicone based and should not be used in our systems. DOT 5.1 is a glycol based synthetic and is fine in our systems....you can use the valvoline synthetic which is essentially 5.1, but they do not call it that....it is called synthetic and exceeds the boiling points of DOT 3 and 4 (wet and dry). Make sure that whatever you use it notes that it is compatible with DOT 3 and DOT 4 (the valvoline says so). I believe they did not want to label it as 5.1 for fear of confusion with 5.0 (they would be right!)
 

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bigdad is right.

However, Volvaline SynPower Brake Fluid's wet boiling point doesn't make it pass then DOT 5.1 standard.

DOT 5.1 is better than DOT3 and DOT4 in all aspects except:
1. Price: Cuz not many ppl use them. Also, they are synthetic so they are more expensive.
2. Not compatible with mineral based DOT3 and DOT4 fluids. But, why would you want to add DOT3/DOT4 fluid just to tap off the resevoir?
3. Easier to absorb moisture. However, even when they are really wet, they still have a higher boiling point than dry DOT3. Besides, it's better to change your resevoir seal and brake line while you are at it, so you shouldn't have to worry too much about moisture. If you are really worried about it, use ATE fluid. Most professionals recommand ATE for high performance street vehicles. I believe BMW OE fluid is also made by ATE.
(I got Motul 5.1 b/c my local shop was giving them away at only $7 a bottle :p )

here's a link for comparason http://www.swedishbricks.net/700900FAQ/Brake Fluid Comparison.htm

SpeedDemon, I got Motul 5.1 when I changed to SS brakelines, so I don't know if just changing the fluid would help to achieve a stiffer pedal. What I've noticed is that my ABS now works much more often/aggressive after I changed all brake/ABS fluids to 5.1:D I need Tires with more grip than my current set now:D
 
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Discussion Starter · #7 ·
Hahaha, I think that I'll probably end up getting the ss lines and the dot 5.1 fluid as long as my master cylinder is ok. If my master cylinder is messed up then I'll just stick with Dot 4 and my rubber lines :p.
 

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if your master cylinder fails, it's because of age and improper bleeding method. Not because of the 5.1:cool:
 

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Refer to this post on the Acura Legend Forums in regards to Dot 5 Brake Fluid

SpeedDemon said:
I noticed on the brake fluid thing in our cars that it says to use either Dot 3 or Dot 4 brake fluid a while back when I needed to add some. What is the difference between the two or which one should I use?
 

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I use the valvoline synthetic for a few reasons.
1) it has much better wet and dry than DOT 3 or 4
2) it is not that much more expensive (I think the last 12 oz can I bought was $3 or so.
3) I don't worry too much about wet rating, since I change fluid every year and get rid of the moisture
4) valvoline is a respected product and easy to find at most parts stores....they don't claim 5.1 rating, but they do exceed DOT 3 and 4 and the difference is minimal.
 
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