“No corrosion because of no water in the system”
If anyone believes this statement, then, they have never understood how a braking system operates.
All braking systems normally operating on DOT 3 or DOT 4 have a connection with atmosphere through the reservoir, if at any time (nearly always) the atmospheric conditions are water saturated, condensation will be present inside the reservoir. This condensate may not mix with DOT 5 or DOT5.1 but it will separate and corrode interior surfaces. So, DOT 5 fluids do not prevent corrosion.
In June 2019, I wrote the following on a Rolls-Royce / Bentley forum, which is self-explanatory.
“…….There is enough evidence Worldwide to show potential incompatibly between brake seals and certain fluids. In practice a vehicle may be converted to Dot 5 and fitted with compatible seals operating without trouble, except for say long pedal travel issues. At some point along comes the mechanic, or the next owner and some brake hydraulic parts get replaced and/or Dot 4 added to the system. The scenario is that the original source of many of the parts and particularly rubber type seals cannot be traced and the rest is history as brake seals fail.
One very well-known case in various circles was when this happened to the R-R car previously used by the prime minister of Australia when Dot 5 was in the system and the rubbers swelled up.
If an injury or fatality occurs through brake failure with a car using incompatible brake fluid, no insurance company I know will fully cover that event. Incompatible here means also when any rebuilder’s instructions have been ignored. In my experience rebuilders of brake parts are very wary of Dot 5 fluid and nearly always wisely state a case of voided warranty if it is used. On a more personal note, a Coroner would not be too impressed neither.
Next, XXXXXX mentioned…. “as the US military and NATO have been using it for years”
I am afraid that is incorrect……my experience with armed forces tells me that the US Army, although initially supported development of Dot 5, very, very, quickly back pedalled on that issue. They did not take well to having some 4000 to 5000 trucks disabled at one hit. (Tip….when you are in that deep you put them all down a stripping and rebuild line to change the affected parts).
Having worked as a consultant and engineer, not only on USA equipment but also in Russia I can tell you their Armies and Air forces all use Dot 4, with good reason. If you doubt that then consider that one hour ago I spoke to maintenance at USAF deliberately and they confirmed my data….they use Dot4!!
I have witnessed a Dunlop 22 inch diameter disk brake (you think you have big Dunlop discs!) used on a Chieftain tank slewing brake lock up when the calliper jammed (same calliper as Jaguar) on a Dot 5 test. No good for any Army, let alone NATO.
It boils down to the fact that if you are 100% happy with compatibility issues you might use Dot 5. If on the other hand you know and have seen first-hand the problems, you will not be going anywhere near Dot 5.
The average owner has no way of evaluating elastomer compatibility with brake seals and thereby lies the danger, compatible with some….not compatible with others.
Your mileage may vary……