brake flush, upgrade to dot 4 or stay with dot 3

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hey guys i have a 2003 hummer h2, and the brake fluid is a light greenish color so i am going to be replacing it and also getting a new master cylinder as mine is leaky. the truck has 240,000 km on it and i assume it has always had the delco supreme 11 dot 3 fluid in it. now since i am already going to be putting brand new fluid in. should i upgrade to a dot 4? or just stay with a dot 3? and if i do stay then is it best just to go with the delco again? i dont tow or anything, just highway and city driving.

i am not a brake expert but i dont want leaks to happen or some new problems if i introduce dot 4 in the system so ill just go with the consensus vote

thanks!
 
I "upgraded" to DOT 4 in my three vehicles calling for DOT3. I saw no reason not to.
 
sounds good, and is it fine to go with JOHNSEN'S Premium or should i go with delco?

thx
 
Why not 5.1??? Higher numbers are ALWAYS better!

In all seriousness, if you don't need the higher boiling points, it won't matter at all. Simply changing your brake fluid is infinitely better than what most people do.
 
Not sure how DOT 4 is an "upgrade" from DOT 3. I guess going from 17-year old DOT 3 to brand new DOT 4 is an upgrade though but so would using new DOT 3.
 
Originally Posted by hallstevenson
Not sure how DOT 4 is an "upgrade" from DOT 3. I guess going from 17-year old DOT 3 to brand new DOT 4 is an upgrade though but so would using new DOT 3.


What about DOT 4 doesn't seem like an upgrade to you?
 
While there may be chemical differences, it's questionable how much benefit they offer. Car manufacturers were still spec'ing DOT 3, and some may still, and that's not necessarily an endorsement, they don't seem to see any real benefit with DOT 4. Otherwise, DOT 4 has a slightly higher boiling point. So what ? How many people boil their DOT 3 fluid ?
 
As you progress through DOT 3, Dot 4, DOT 5.1, in general while the boiling point goes up, so does the propensity to absorb water. On that basis DOT 3 would need changing less often which is a plus point.
 
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I'd just stay with DOT 3.
Originally Posted by barryh
As you progress through DOT 3, Dot 4, DOT 5.1, in general while the boiling point goes up, so does the propensity to absorb water. On that basis DOT 3 would need changing less often which is a plus point.



barryH knows what he is talking about. I'd just stay with DOT 3.
 
Originally Posted by Gebo
I'd just stay with DOT 3.
Originally Posted by barryh
As you progress through DOT 3, Dot 4, DOT 5.1, in general while the boiling point goes up, so does the propensity to absorb water. On that basis DOT 3 would need changing less often which is a plus point.



barryH knows what he is talking about. I'd just stay with DOT 3.


There are some questions with older Japanese vehicles where DOT4 has certain additives that can cause seals to fail. Older probably being 1980s and earlier but possibly a bit later too maybe into the early 90s. When in doubt stick with the spec a car originally came with.
 
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