Halo by Orthene GT DOT 4 Racing Brake Fluid 600ml

Halo by Orthene GT DOT 4 Racing Brake Fluid 600ml – 336°C Dry Boiling Point, Ultra-Low Viscosity for Club Racing, Track Days and Fast Road

Halo GT is a DOT 4 racing brake fluid from Orthene, the British company that makes much of the world's motorsport brake fluid. It is based on the chemistry of Halo P1, Orthene's flagship professional race fluid, but it is fully DOT 4 compliant. That means you get race-level heat resistance in a fluid you can also run on the road. With a typical dry boiling point of 336°C and a wet boiling point of 206°C, it is aimed at club and sprint racers, committed track day drivers and fast road cars whose standard fluid starts to go soft after a few hard stops.

What sets GT apart is its very low viscosity for a high-boiling fluid: 1350 cSt at -40°C, well inside the 1800 cSt DOT 4 limit. A thinner fluid moves through the lines, ABS modulator and caliper more quickly, so pressure builds faster when you hit the pedal and the pistons retract more cleanly when you come off it. Halo says this gives sharper, more precise modulation into the corner and less drag on the exit. GT is optimised for modern ABS-equipped performance cars.

GT also uses Orthene's Fade Resistant Technology™, which is designed to keep the pedal feel consistent through repeated heat cycles as temperatures rise session after session. Every bottle is developed, manufactured and quality controlled by Orthene in the UK.

Technical Specifications

• Manufacturer: Halo by Orthene
• Part Number: GTEUK198L2
• Specification: DOT 4
• Dry Equilibrium Reflux Boiling Point: 336°C (637°F) typical
• Wet Equilibrium Reflux Boiling Point: 206°C (403°F) typical
• Kinematic Viscosity at -40°C: 1350 cSt
• Kinematic Viscosity at 100°C: 2.5 cSt
• pH: 7.15
• Volume: 600ml
• Made In: United Kingdom

Figures are typical values published by Halo by Orthene for fresh fluid. The wet boiling point is measured after the fluid has absorbed a set amount of moisture under the standard DOT test method.

Key Features

• 336°C typical dry boiling point, which is very high for a DOT 4 fluid and resists vapour lock and a long pedal under repeated heavy braking.
• 206°C typical wet boiling point, so it keeps a big safety margin as it absorbs moisture over time.
• Ultra-low viscosity (1350 cSt at -40°C) for faster hydraulic response, more precise modulation and quicker piston release.
• Fully DOT 4 compliant, so it can be used on the road as well as on track.
• Optimised for modern ABS systems on performance cars.
• Fade Resistant Technology™ for a consistent pedal feel through repeated heat cycles.
• Derived from Halo P1, Orthene's professional-level race fluid.
• Developed, manufactured and quality controlled in the UK.

What's in the Box?

• 1 x Halo GT DOT 4 Racing Brake Fluid, 600ml sealed bottle

Fitment

Universal. Suitable for vehicles and brake or clutch hydraulic systems that specify a DOT 3, DOT 4 or DOT 5.1 glycol-based fluid. Always check your vehicle manufacturer's recommended fluid first.

Not suitable for: systems designed for silicone-based DOT 5 fluid, or systems that use mineral oil (LHM), such as some older Citroën hydropneumatic cars. For professional race cars that need the highest boiling point, see Halo P1 Racing Brake Fluid.

Installation

For the full benefit, flush the old fluid out of the system completely rather than just topping up. Bleed each corner in the order your vehicle manufacturer specifies, which is usually starting furthest from the master cylinder. Cars with ABS may need a diagnostic tool to cycle the ABS pump during bleeding. Brake fluid damages paintwork, so cover painted surfaces and wipe up any spills straight away with plenty of water. Brakes are safety-critical, so we recommend having the work done by a competent mechanic if you are unsure.

Upgrade Further

Running a professional race car or endurance programme? Halo P1 is Orthene's flagship race fluid, with a 341°C typical dry boiling point, and is used by teams in BTCC, IndyCar and endurance racing.

Is Halo GT legal for road use?

Yes. Halo GT meets the DOT 4 specification, so you can use it in road cars that call for DOT 4 fluid, as well as in track and competition cars.

What is the difference between Halo GT and Halo P1?

GT is based on P1's chemistry and is designed for club and sprint racing, track days and fast road use, while staying fully DOT 4 compliant. P1 is Orthene's no-compromise fluid for professional motorsport, with an even higher dry boiling point. For most track day and club racing cars, GT is the right choice.

Can I mix it with my existing brake fluid?

GT is a DOT 4 fluid, so it can be mixed with other glycol-based DOT 3, DOT 4 and DOT 5.1 fluids. However, mixing it with old or lower-spec fluid will lower its boiling point. To get the full benefit, flush the old fluid out completely. Never mix it with silicone-based DOT 5 fluid.

How much fluid do I need?

A full flush and bleed on most cars uses about 1 litre, so two 600ml bottles are usually enough. Cars with a shared clutch reservoir, twin master cylinders or a hydraulic handbrake may need more. It's worth keeping a spare sealed bottle for bleeding between sessions.

How often should I change it?

All glycol-based brake fluids absorb moisture over time, which gradually lowers the boiling point. For track and race use, bleed the brakes before each event and replace the fluid fully at least once a season. On a fast road car, a full change every 12 months is sensible, or follow your vehicle manufacturer's service interval if that is shorter.

Can I use it in my hydraulic clutch?

Yes. If your clutch shares the brake reservoir or specifies DOT 4 fluid, you can use Halo GT in it.

Will a lower viscosity make a difference on a road car with ABS?

Yes. A lower viscosity lets the fluid move through the ABS modulator and brake lines more easily, especially when cold. This helps the pedal respond faster and more consistently. GT is optimised for modern ABS-equipped performance vehicles.

How should I store an opened bottle?

Keep the cap tightly closed, and store the bottle upright in a cool, dry place. Once it's been opened, the fluid starts absorbing moisture from the air, so use it promptly. For competition use, a fresh bottle each time is best.