Brake Fluid Guide: DOT 3 vs DOT 4 vs DOT 5 vs DOT 5.1
October 24, 2026 · RPS Distributors
Brake fluid is easy to forget, but it is one of the most important safety fluids in a vehicle. It carries the force from the brake pedal to the calipers and wheel cylinders. If the fluid is old or the wrong type, braking performance can suffer.
The DOT ratings
| Type | Base | Can it mix with DOT 3/4/5.1? | Typical use |
|---|---|---|---|
| DOT 3 | Glycol | Yes | Many cars and light trucks |
| DOT 4 | Glycol | Yes | Many European and newer vehicles; higher boiling point than DOT 3 |
| DOT 5.1 | Glycol | Yes | High-performance applications; highest boiling point of the glycol fluids |
| DOT 5 | Silicone | No | Some classic and specialty vehicles |
The higher the DOT number among the glycol fluids, the higher the boiling point. In general, DOT 4 can be used where DOT 3 is specified, but always check the vehicle's requirements.
Never mix DOT 5 with the others
DOT 5 is silicone-based. It does not mix with DOT 3, DOT 4 or DOT 5.1. Mixing them can cause poor braking and seal problems. Only use DOT 5 in systems designed for it.
Why brake fluid needs changing
Glycol brake fluids absorb moisture from the air over time. Water in the fluid lowers its boiling point and can cause corrosion inside brake lines and calipers. Many manufacturers recommend a brake fluid flush every two to three years — check the service schedule.
Handling tips
- Keep containers tightly closed so the fluid does not absorb moisture.
- Brake fluid can damage paint — wipe up spills right away.
- Never reuse old brake fluid.
Brake fluid at wholesale prices
RPS Distributors carries brake fluid from Lucas, STP, Castrol, Johnson and Super S. Browse the Fuel Additives collection, where our brake fluids are listed by brand.
Request a wholesale quote or call 1-855-498-7509.