Disco 2 Brake Fluid - low viscosity or not

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Disco Magic

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Don’t know if I’m overthinking this but as I’m about to flush the brake fluid should I use good quality standard Dot 4 or low viscosity (Dot 4 Class 6)?

It’s seems LV brake fluid is recommended for vehicles with ABS / TC and ESP if fitted. My 2006 Freelander 1 specifies Shell ESL Donax EB which is a Dot 4 class 6 fluid.

I believe the Disco 2 had Castrol GLMA from the factory but is anyone here running Dot 4 class 6 LV brake fluid?
 
From what I’ve read any benefit of LV would only be felt when the modulator is actually activating ABS/TC etc, no benefit under normal braking.

I’ll go with standard/classic Dot 4 this time seeing as Class 6 isn’t specified.
kermit_rr said:
The dot 4 class 6 stuff is better known as dot4+ or super dot4.
Unless you know you need it, use the normal dot 4 (class 4)
Dot4+ has a higher dry boiling point
Click to expand...
Yes, I went down the boiling point rabbit hole too.

The handbook specifies a minimum boiling point of 260°.

DOT 4 is minimum 230°
DOT 4+ is minimum 260°

For added confusion some standard DOT 4 is well in excess of 260° without being designated “+”.

Class 6 isn’t the same as DOT 4+, Cl 6 is specifically Low Viscosity although does have the higher boiling point.

Who’d have thought brake fluid could be so varied. 😂
 
Last edited:
discool said:
Yes use the standard DOT 4, my old RR used it so been around for a longtime. Even a Maserati I had use DOT4.

Although not that i’m interested but to find out, my quick Google search states DOT 4 Class 6 was introduced as an American spec.☹️
Click to expand...
All of the DOT standards are based on the American FMVSS 116 specification - DOT being the American Dept Of Transport.

Class 6 is a low viscosity variant of DOT 4

I’ll stick with straight DOT 4, I expect if LR had wanted D2’s to switch to LV brake fluid after the handbooks were printed there’d have been a TSB to that effect.
 
I use one of these to take the guesswork out when trying to determine the quality of the fluid in the vehicle and in containers, even those that are still sealed. It is normal for it to report water content >4% when testing fluid that has been in the vehicle for 2 years or so. Which is precisely the change interval according to LR's maintenance schedule.

Amazon product
 
NPG said:
I use one of these to take the guesswork out when trying to determine the quality of the fluid in the vehicle and in containers, even those that are still sealed. It is normal for it to report water content >4% when testing fluid that has been in the vehicle for 2 years or so. Which is precisely the change interval according to LR's maintenance schedule.

Amazon product
Click to expand...


good call as also got one of those

did have a litre of brake fluid in the shed that was stored for around a year , lid on tight but alas failed when using one of those testers so indeed a great product to take the guess work out as u also mention
 
Plus this is the stuff that I normally use for my D3

IMG_6297.jpeg
 
kermit_rr said:
I don't have a tester but just go off the colour
Click to expand...

Colour is also a good indicator of fluid quality. I've also seen claims that UV from sunlight causes fluid degradation. Never came across any scientific tests that provide evidence of this but I once did have Halfords DOT4 fluid, which came in a black 5L container with a recommendation to store it away from sunlight. So there might be some truth in that claim after all !
 
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