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Castrol SRF vs. Halo P1 by Orthene: Which Racing Brake Fluid Should You Choose in 2025?
For decades, Castrol SRF Racing Brake Fluid has been a gold standard in motorsport. But with recent price increases, many teams and enthusiasts are searching for alternatives that offer similar or better performance without the premium cost. One standout contender is Halo P1 by Orthene Specialist Racing Brake Fluid.
Technical Comparison
| Specification | Castrol SRF | Orthene Halo P1 |
|---|---|---|
| Dry Boiling Point | ~310–312°C (590–594°F) | 341°C (646°F) |
| Wet Boiling Point | ~270°C (518°F) | 206°C (403°F) |
| Viscosity @ –40°C | ~1300 mm²/s | ~1400 mm²/s |
| DOT Classification | DOT 4 Racing | DOT 4 Racing |
| Typical Use Cases | Endurance racing, long intervals between flushes | Track days, sprint racing, budget-conscious competition |
Performance Considerations
Temperature Resistance
Halo P1 has a higher dry boiling point, which can be beneficial in sprint formats or track days where extreme heat is generated over short periods. SRF’s slightly lower dry point is offset by an exceptional wet boiling point, making it more resistant to moisture-related boiling over time - a key advantage in endurance racing.
Service Intervals
Castrol SRF’s high wet boiling point allows for longer intervals between fluid changes, which can be advantageous for teams running multiple endurance events per season. Halo P1, with its lower wet point, is best suited for shorter maintenance cycles and ideal for track enthusiasts who bleed their brakes regularly.
Price and Value
Recent market shifts have seen significant price increases for Castrol SRF. This makes Halo P1 an attractive option for teams and individuals who want top-tier dry boiling performance at a more competitive price.
Our Recommendations
- If you run endurance races or want maximum time between brake fluid changes: Choose Castrol SRF.
- If you do frequent track days, sprints, or short-format races: Choose Halo P1 by Orthene for higher dry boiling point and cost savings.
Learn More
- Explore the full Racing Brake Fluid Buyer’s Guide for all top options
- Read our Track Day Brake Fluid Guide
- Check our Endurance Racing Brake Fluid Guide