Great, thanks @Zirconblue.

I will get to it when I have the time. need to swap my front discs and will be using EBC Red Stuff pads as an experiment as I loved them on the BMs

Zirconblue wrote:

Or DOT 5.1, it's a higher specification - higher temperature resistance. - Usually more expensive, but sometimes you find deals where it's cheaper.

If i remember correctly DOT 5 can't be mixed with DOT 4, but DOT 5.1 can. So i think they're saying you have to flush the whole system through if you use DOT5, you can't just top up DOT 4 with it.

It doesn't help the DOT rating system for brake/clutch fluid isn't very intuitive.
I did a load of research into brake fluids about 15 years ago for use in my track cars.

DO NOT USE DOT 5 FLUID...it's silicone based, it has a completely different chemical make up than normal glycol fluid (DOT 3, 4 or 5.1) and they are totally incompatible with each other.

You can use DOT 4 or DOT 5.1 in the L322.
However it's a misconception that a DOT 5.1 fluid is better performing than every DOT 4 fluid.
DOT 5.1 standard was introduced to cope with certain modern ABS systems with micro valves that required a thinner viscosity fluid and that is reflected in the specification. The minimum specs of DOT 5.1 are indeed higher than DOT 4 however that doesn't mean in the important criteria - wet and dry boiling points - that a DOT 5.1 fluid will be better performing than a decent DOT 4 fluid. The specs are a minimum requirement and often DOT 4 fluids surpass the minimums by quite a margin but can't pass the viscosity criteria of DOT 5.1 so are rated as DOT 4.
If your braking system doesn't require DOT 5.1 fluid then you don't need a DOT 5.1 fluid and you should then look for the wet and dry boiling points instead. Dry boiling point is fresh fluid rating, wet is after 3.7% of water has been absorbed which reduces the boiling point and is typical after some time in the system - it's the important rating.

A typical example is what is regarded the best brake fluid in motorsport - Castrol SRF Racing. It's rated as DOT 4 however it has one of highest wet and dry boiling points of any brake fluid (320C dry, 270C wet) and far above the DOT 5.1 wet and dry boiling point minimum specification (260C dry, 180C wet). Another top performer in motorsport is Motul RBF600/660, again it's DOT 4 rated.

As others have mentioned ATE Racing Super Blue is, or should I say was, a very good fluid. ATE Typ200 is exactly the same fluid but is yellow (it has exactly the same specs as Racing Blue). The idea behind it was you could swap between the two fluids on consecutive fluid changes and know when the fluid has been bleed through...unfortunately I guess some dimwits decided the blue colour could be confused with antifreeze.
Other decent fluids are Castrol Response DOT 4 or Super DOT 4, Super DOT 4 is a fluid that's been treated with boric acid which helps to make it last longer (has a better wet boiling point).

At the end of the day unless you are doing trackdays in your Range Rover you are unlikely to boil your brake fluid, any half decent DOT 4 or DOT 5.1 fluid will suffice. Just remember that a DOT 4 may be better than a DOT 5.1 fluid in the important specs so read up on the wet and dry boiling points, the higher the better. Don't pay extra for a DOT 5.1 fluid thinking it's better, in most cases it won't be.
Also make sure the brake fluid is changed every 2 years, the water absorbed into the fluid will downgrade the fluid performance and can corrode components internally.
Only buy enough fluid for what you need and get it fresh from a decent supplier that goes through stock regularly. Glycol fluids are hygroscopic and absorb moisture, even through the plastic of their container while sitting on a shelf. It's why decent fluids used to come in metal containers (SRF changed to plastic a few years ago, ATE still use metal I think).

I hope that's clarified some points!

Good info there. I only raised the issue of 5.1 as sometimes you get it cheaper.

Silicone fluid (DOT 5) is as i recall mega expensive. It has advantages (it doesn't strip paint for example) but it's never really caught on.

Quote:

The idea behind it was you could swap between the two fluids on consecutive fluid changes and know when the fluid has been bleed through...unfortunately I guess some dimwits decided the blue colour could be confused with antifreeze

Quote:

It's why decent fluids used to come in metal containers

Stops you keeping it so long, because the tin normally rots out and when you pick it up one day the bottom falls out complete with fluid.

I used silicon fluid in the newly refurbished brake system on a Lotus Éclat I restored. I couldn't understand why the brakes kept on binding and spoke to Lucas who had supplied the master cylinder. The guy was scratching his head until I mentioned silicon fluid. 'That's your problem' says he, and he was correct!

Fluid drained, flushed and replaced with DOT4; problem solved. It causes swelling of the seals he said, and prevented the pistons from returning easily.

mat777 wrote:

Hmm, that sounded intriguing.

I went and googled it, it appears unfortunately that it is no longer available. Lots of listings for ATE non-coloured fluid on ebay, all say "ATE TYPE 200 Brake Fluid not Super Blue - Unfortunately due to EU & US law brake fluid can no longer be supplied in blue. This ATE Type 200 is the same spec as the "Super Blue" but amber in colour to meet the new rules."

Is the Eu so far up its backside now that it has got to the point of regulating what colour brake fluid ought to be?

Yes it is the same but given that Super Blue is no longer listed on the ATE website (it's replaced by Typ200) it's more than likely old stock so I wouldn't bother.
When I used to use it I would get it from GSF but I see now they only stock Typ200 @£17/litre (£14 if ordered online and collected in store using code CC20).

I should add the ATE Typ200 (and Super Blue before it) are also quite long lasting, ATE quote up to 3 years although I would still change it at 2 years.

Just use Typ200 or cheaper alternatives with good spec/price are Castrol React Performance (formerly Response Super DOT 4) @ £12/litre or just Castrol Brake Fluid DOT 4 (formerly Response DOT 4) @ £10/litre (prices from Opieoils.co.uk).