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Inform the uninformed - Brake Fluid Dot 3 or dot 4

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  #1  
Old 12-14-2010, 11:39 PM
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Inform the uninformed - Brake Fluid Dot 3 or dot 4

I own a 2004 with 5.4. I want to change the brake fluid. The top of the brake fluid cap says to use dot 3. Of course, I want the best for my truck. Should I buy Dot 4 brake fluid?

I searched the forum and didn't see the answer to this simple question.
 
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Old 12-15-2010, 12:15 AM
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3 and 4 are pretty much the same. just dont use dot 5, that wont work thats motorcycle and racing applications most of the time. 5 is synthetic i believe. most bottles you buy say dot 3&4 on them.
 
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Old 12-15-2010, 09:32 AM
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Last edited by 05RedFX4; 12-15-2010 at 08:23 PM.
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Old 12-15-2010, 10:27 AM
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Good points. I will stick with 3
 
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Old 12-15-2010, 12:12 PM
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There is some misinformation in this thread.

Dot 5 is silicone based, not Dot 4. Dot 3 and Dot 4 brake fluids are both glycol based.

Don't use Dot 5 in your truck, use either Dot 3 (recommended) or Dot 4. The main difference between Dot 3 and Dot 4 brake fluids is that Dot 4 has higher wet and dry boiling points so it's better than Dot 3 for applications where the brake fluid can expect to get hot, such as on race cars. I think you'd be wasting your money using Dot 4 in your truck, assuming that you are driving it like 99.9% of F-150 owners. It won't hurt but isn't necessary.
 
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  #6  
Old 12-15-2010, 02:58 PM
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Originally Posted by MikeColangelo View Post
There is some misinformation in this thread.

Dot 5 is silicone based, not Dot 4. Dot 3 and Dot 4 brake fluids are both glycol based.

Don't use Dot 5 in your truck, use either Dot 3 (recommended) or Dot 4. The main difference between Dot 3 and Dot 4 brake fluids is that Dot 4 has higher wet and dry boiling points so it's better than Dot 3 for applications where the brake fluid can expect to get hot, such as on race cars. I think you'd be wasting your money using Dot 4 in your truck, assuming that you are driving it like 99.9% of F-150 owners. It won't hurt but isn't necessary.
X 2: Also (just to add a little information here), the DOT 4 is a little less likely to draw moisture (a common trait of brake fluid). If you have a vehicle that sets a lot, the DOT 4 is a good bet. BTW, Wal-Mart sells the DOT4 for just a few pennies more than the DOT 3. I use the DOT 4 in my '91 Mustang, because it doesn't get out much between cruises and car shows.
 
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Old 12-16-2010, 12:15 PM
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Unless you thouroughly research it, I would suggest you stay with the manufacturer recommended.

Here is a ton of information
http://www.stoptech.com/tech_info/wp...fluid_1a.shtml

of particular note from that website
DOT 4 fluids are also glycol ether based, but have a measure of borate esters thrown in for improved properties including increased dry and wet boiling points. A seldom talked about characteristic though is that because of this chemistry, the DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically once the fluid does actually begin to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3. By FMVSS116 standards, DOT 4 fluids must have a minimum dry boiling point of 446F and a minimum wet boiling point of 311F.

Does this make DOT 4 fluids better than DOT 3 fluids? Not always. Remember, the boiling points listed are minimums and there are DOT 3 fluids out there with higher boiling points than some DOT 4 fluids. The real differentiating factor should be that if you run a DOT 4 fluid you really should change the fluid more often than if you use a DOT 3, if for no other reason than the rapid fall off in boiling point with time.
 
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