DOT 3 lasts longer than DOT 4 because it lacks the esters?

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I read it lasted longer somewhere, I'm not sure why though. I change it every 2 years or so, so for me the point is moot. I would rather have the higher boiling point offered by the DOT4 fluid.
 
The higher boiling point is more hydrophilic is what I figured. A trade off, marginally better performance for more maintenance. Lotsa guys bleed their track cars between events.
 
There are TWO types of DOT 4 brake fluid. One is DOT 4 LV. Some European brands and Ford and Lincolns specify a DOT 4 LV brake fluid.

 
By definition all DOT 4 meets the specifications of DOT 3, it just costs a little more to make. Same for Dot 5.1, not to be confused with Dot 5. There is a chemical difference between fluids. So there is nothing special about labeling a DOT 4 fluid DOT 4/3. Some folks like me just will not buy it, most must or they would quit doing it.

Dot 4 does normally absorb moisture a little faster.

There are also not regulated by DOT additives to control foaming, lubrication and corrosion. GM brake fluid used to be better at preventing corrosion that some other brands. I change my fluid every 2 years now so that point is moot and I have no recent information.

Rod
 
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I think they are all polyethylene glycol and therefore ALL brake fluids are synthetic. What varies is the molecular weight or chain length of the molecules. The higher the molecular weight, the higher the boiling point and the thicker the viscosity. Being a polyether, they are all hygroscopic but they do not attack rubber! So seals and rubber brake lines are kept intact with no swelling.
 
Originally Posted By: benjy
prolly the opposite as ester based fluids are superior.


Sounds like a very generic comment with zero basis.
 
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