Motul DOT 5.1 anomaly

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Aug 27, 2006
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Atop a hill above Portland, Oregon
We are in the midst of a brake upgrade. Two years ago, we bought a ten year old Infiniti EX37 Journey AWD, with 38,000 miles on the odo. which, according to Carfax, had been serviced exclusively at Infiniti dealerships for all of its service life. (And the previous owner had anticipated service intervals: for instance, having the 30,000 mile service done at 25,000 miles.) So far, the vehicle has served us well, but, when we took the car into our longtime and trusted mechanic in October 2022, when we picked up the car, the service order stated that, "We (the service shop) should take a peek at the rear brakes the next time you bring the car in." From that note, we deduced that — probably — the car was on its second set of front rotors and pads, as, even though the front rotors are larger than the rear rotors, they usually wear faster than the rears due to transfer of mass during braking. So a week ago, we had new rotors (EBC BSD7351, which are "high carbon" slotted rotors) and pads (Stoptech 309 series para-aramid pads) installed at the rear of the EX37. As part of the installation, we began the incremental process of replacing the Nissan factory fill DOT 3 brake fluid with Motul DOT 5.1 brake fluid. We had the first drain-and-fill last week, and are scheduled to have two more drains-and-fills in coming weeks, gradually replacing the old DOT 3 fluid with modern DOT 5.1 fluid over the next month.

Here is the anomaly: we purchased the Motul DOT 5.1 brake fluid from two different sources. As we understand it, Motul has offered DOT 5.1 fluid for sale only recently. The bottles that we have on hand were sealed, and appear to be fresh and uncontaminated. BUT the dry boiling point claimed by Motul on the front of the three bottles are all different from each other. One bottle has printed on the front that the dry boiling point is 516°F., a second has a stated dry boiling point of 518° F., and the third has a stated dry boiling point of 522° F. For the mathematicians among us, that amounts to a spread of only 6° F. among the three bottles, which is nothing to worry about, and we are not worrying.

Still, there must be a real cost, albeit a minor one, for Motul to have bottles printed up with different specifications printed on the fronts of the bottles.

Does anyone care to venture why the printed specs on the bottles would differ?
 
. As we understand it, Motul has offered DOT 5.1 fluid for sale only recently.
where did you get that notion? Or by recently, do you mean in the last 5 years? Actually, I just googled and found some discussion of their 5.1 vs their racing brake fluid dating back to 2006. But, yeah, the labeling differences are a bit weird. I can see this stuff sitting on a shelf for quite awhile though. Heh, maybe the bottle senses how long it’s been sitting on the shelf, and automatically changes itself to a lower boiling point the longer it sits. 😂🤣. I’d be more inclined to believe the formula has changed, or the different bottles were intended for a different market, or maybe one is counterfeit??? Then again, maybe the French are more anal about their labeling, and each bottle was actually tested, and labeled accordingly 😂🤣😂
 
Motul has had 5.1 for a while, I'd be concerned about how old some of your bottles are.

Just some conversation but Bosch ESI6 is a great alternative and designed for extended intervals which might be a better fit for your car. Though the price has almost doubled in a year.

Stoptech 309 pads are awesome I put them on all my vehicles including my Jeep :D they are dusty but are great! What do you have up front?
 
Just some conversation but Bosch ESI6 is a great alternative and designed for extended intervals which might be a better fit for your car. Though the price has almost doubled in a year.
Stoptech 309 pads are awesome I put them on all my vehicles including my Jeep :D they are dusty but are great! What do you have up front?
We have a passel of bad experiences with Bosch, although mostly with mechanical devices, not with fluids. We had a terrific, powerful Bosch countertop blender that worked for a while, then one day the connection between the container and the motor base started spinning uncontrollably; turned out that critical interface was naught but a cheap nylon gear. Contacted Bosch, and was told that Bosch did not have, and never had stocked, a replacement part for the stripped gear; the blender was therefore absolutely useless. We had a 1400 watt German-made Bosch canister vacuum cleaner. One day, the control to adjust the motor speed broke off at the neck. Same story: just a little piece of plastic, but we could not get the appliance repaired; Bosch advised us that it never had stocked any replacement parts for its vacuum cleaners; vacuum cleaners were regarded as disposable items. We had a Bosch wall oven . . . well, you get the point. From our experience we think that Bosch does not give a **** about its customers. We never again will buy any Bosch product. I certainly would not expect Bosch to stand behind its extended interval claims for the ES16 fluid.

There are a lot of reviews on Amazon and elsewhere that say that 309 series StopTech pads dust badly; there are almost as many that say that the same 309 series pads are very low dusting pads. In creating dust, it takes two to tango: the rotors and the pads, and -- still lacking extensive experience of our own -- we can only wait and see how that dichotomy works out. My suspicion, NOT based on facts in the field, is that the difference in opinions about 309 series pad dusting may relate to the rotors with which the StopTech pads are used; that is, that the dust probably comes more from the surface of the rotors than it comes from the surface of the pads. Of course, I may be wrong. In the short time that we have had the StopTech pads on the rear brakes of the Infiniti, they are definitely a performance upgrade from the OEM Akebonos, which we assume are what currently are on the front of the car, as the Carfax report indicates that the previous owner apparently always took it to an Infiniti dealership when service was needed.
 
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There are a lot of reviews on Amazon and elsewhere that say that 309 series StopTech pads dust badly; there are almost as many that say that the same 309 series pads are very low dusting pads. In creating dust, it takes two to tango: the rotors and the pads, and -- still lacking extensive experience of our own -- we can only wait and see how that dichotomy works out. My suspicion, NOT based on facts in the field, is that the difference in opinions about 309 series pad dusting may relate to the rotors with which the StopTech pads are used; that is, that the dust probably comes more from the surface of the rotors than it comes from the surface of the pads. Of course, I may be wrong. In the short time that we have had the StopTech pads on the rear brakes of the Infiniti, they are definitely a performance upgrade from the OEM Akebonos, which we assume are what currently are on the front of the car, as the Carfax report indicates that the previous owner apparently always took it to an Infiniti dealership when service was needed.

Slotted/drilled rotors will cause more dusting as the edges will cut into the pads more but initial bite will be improved (although the "improved" feel may not realistically be felt at all.) With that said, I have found the StopTech 309s (also called Stoptech Sports) to have a lot of dust for what they are.
 
Did you check date of production on the bottles?
Got to it this morning. The two dry boiling point = 522° F. bottles have a date of 9.5.22, which in the U.S. usually means September 5, 2022, but in France, where the bottles were filled, it could well mean May 9, 2022. The dry boiling point = 516° bottle reads 11.06.21, which means either November 6, 2021, or June 11, 2021. The dry boiling point = 518° bottle was disposed of in the mechanic's trash, so I do not know the date on it. At the time of purchase, all of the bottles were securely hermetically sealed.
 
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Got to it this morning. The two dry boiling point = 522° F. bottles have a date of 9.5.22, which in the U.S. usually means September 5, 2022, but in France, where the bottles were filled, it could well mean May 9, 2022. The dry boiling point = 516° bottle reads 11.06.21, which means either November 6, 2021, or June 11, 2021. The dry boiling point = 518° bottle was disposed of in the mechanic's trash, so I do not know the date on it. At the time of purchase, all of the bottles were securely hermetically sealed.
Motul does not blend brake fluid. For US market, it is done by DuPont, I think. Motul has a formula. So, it is MM/DD/YYYY.
 
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