DOT 4+/Super DOT4 Minimum Dry & Wet Boiling Points

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Aug 30, 2004
I recently had a 2016 MB E350 Sedan come in for its second "B" service at 41K. MB now requires a brake fluid replacement at every "B" service, which occurs every 2 years or 20K miles.

This vehicle specs "DOT4+" brake fluid, which some folks refer to as "Super DOT4." My understanding of "DOT4+" fluid is that it is supposed to carry a higher boiling point than regular DOT 4. I believe this is the only intended difference between "DOT4+" and regular DOT4 fluid.

Pentosin offers a Super DOT4 fluid that carries a dry boiling point of 265C (509F) and a wet boiling point of 165C (329F). My supplier sells Textar DOT4 LV fluid which carries a dry boiling point of 266C (511.8F) and a wet boiling point of 171C (339.8F). ATE also mentions in their marketing literature that ATE SL.6 can replace "Super DOT4" and their SL.6 fluid has a dry boiling point of 265C (509F) and a wet boiling point of 175C (347F).

So, my questions are as follows:

1) It appears that DOT4LV fluids have a superior dry/wet boiling point compared to a Super DOT4 fluid. What is the advantage of using Super DOT4/DOT4+ over DOT4LV?
2) Is there a published spec for minimum dry/wet boiling on DOT4+/Super DOT4 fluids?
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For the record, I flushed the MB using Textar DOT4 LV. I did not see the point of using Super DOT4, unless you folks advise me otherwise.
I'm just guessing at any of this however:

1)It may only be proprietary? I can only assume that the higher boiling point of the Super DOT4 is for the possible higher speeds/harder braking situations and repeatedly.

2) IDK! However, MB's required/suggested brake fluid service of 2 yrs/20K miles may be due to the higher boiling point which may in fact absorb more moisture
DOT4+ is just a made up nonsense spec. DOT4 LV is fine. Trivial differences in temperature are trivial. The important thing is just that the industry slowly evolves the tech and a luxury brand will obviously recommend what's best at the time of the recommendation, even though in real world use it matters very little. What matters is you're covering your *** by at least using DOT4, not DOT3 and obviously not DOT5.

However if your goal is to preserve warranty, you need to use the official fluids not substitutes even if they are exactly the same thing in a bottle with different words stamped on it. If warranty be [censored], any DOT4 is fine. It's going to have other braking problems before a small boiling point difference matters if replaced on a 2 year interval, which in itself is excessive but I digress. Any brake system that doesn't have more margin than that is clearly defective.

Warranty preservation is the answer. Spend money to do that. Save money when it doesn't.
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Legally, there is no such thing as Super DOT 4. The "super" is just a marketing term. FMVSS 116 only defines DOT 3, 4, 5, and 5.1.

That said, Pentosin is good stuff even if a bit pricey. Autozone has a Bosch brake fluid that is also very good. The Textar you can get from your supplier will give you good results with no problems as well
Originally Posted By: PiperOne
Does the LV mean Low Viscosity? Does that matter for an ABS pump?

Yes. LV = Low Viscosity. its's supposed to make the ABS work a little better, particularly when it's cold
My 06 Unimog also "requires" DOT 4+ for the clutch linkage (because it is a MB product). Brakes are air fortunately. MB recommends clutch fluid change every 3 yrs, I stretch it to 5 since it didn't get dirty with tendency to malfunction till 8-9 yrs. My question is this:
since the clutch is NOT a heat buildup area compared to brakes, is there another grade of brake fluid that is compatible with DOT 4 (in other words NOT silicone based DOT 5)
that is LESS hygroscopic than DOT4+ and will therefore last longer in this relatively undemanding application?

Since temperature and viscosity are not an issue with a clutch then DOT 3 is reckoned to be less hygroscopic than DOT 4. DOT 5.1 is the worst in this respect so definitely avoid that.
Originally Posted By: The Critic
What is the advantage of using Super DOT4/DOT4+ over DOT4LV?

Probably a markup advantage for the company selling it.
Personally, given the price I can get Castrol LMA DOT 4 at, there's no reason for me to try anything else of any different spec.
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