What Oil Can Replace Brake Fluid?
3 Answers
Different oils have different compositions and naturally cannot achieve the original effect of brake fluid. If other oils are used as substitutes, not only will the braking performance significantly decrease, but it may even lead to brake failure. Therefore, there is currently no oil that can replace brake fluid. Brake Fluid: Brake fluid, also known as brake liquid or hydraulic brake fluid, is made from refined diesel distillate combined with thickeners and antioxidants. The replacement cycle for brake fluid is 2 years or 40,000 kilometers, but it is still necessary to refer to the cycle specified in the user manual. There are three types of brake fluid: mineral oil brake fluid, alcohol-based brake fluid, and synthetic brake fluid. Brake fluid must have good viscosity-temperature properties, be able to work over a wide and low-temperature range, and possess excellent oxidation stability, anti-foaming properties, resistance to rubber swelling, and rust prevention. Precautions for Using Brake Fluid: Different types and brands of brake fluid should not be mixed. Due to differences in additives or specifications, they may produce different effects during use. If brake fluid absorbs moisture or contains other impurities, it should be filtered and replaced promptly to avoid insufficient braking force during braking, which could affect braking performance. If the vehicle exhibits uneven braking or pulling to one side while driving, it is recommended to conduct a comprehensive inspection of the braking system. If the brake caliper piston seal is found to be excessively swollen, it may indicate a problem with the quality of the brake fluid. In such cases, the brake fluid and seal should be replaced promptly to ensure the normal operation of the braking system. Brake Fluid Replacement Method: Turn off the vehicle and open the engine hood. Use a syringe to extract the fluid from the reservoir until it is empty. Fill the reservoir with new brake fluid. Use a jack to lift the vehicle, starting with the rear wheels, and remove the tires. Locate the brake caliper bleeder screw and remove the rubber dust cap. Use a wrench to loosen the bleeder screw, attach a rubber tube to it, and connect the other end to a drainage bottle.
As a veteran mechanic with years of experience repairing cars, I must emphasize that you should never use any other oil as a substitute for brake fluid. Brake fluid is a specially formulated hydraulic oil, such as the commonly used DOT 3 or DOT 4, which has an extremely high boiling point to prevent boiling and foam formation during intense braking. If you use engine oil, transmission fluid, or any off-brand oil, they will expand and deform due to heat in the brake system, corrode the seals causing leaks, and immediately make the brakes soft and ineffective. I've personally witnessed a customer who tried to save money by using regular engine oil, and the result was terrifying—the brake pedal went all the way to the floor with no response while descending a hill, nearly causing an accident. The brake system is critical for safety and cannot be taken lightly. Always use the exact product grade specified in your vehicle's manual. During routine maintenance, regularly check the fluid because brake fluid absorbs moisture, which lowers its boiling point. Replacing it every two years is the safest practice. Don't risk your safety to save a few bucks—your life comes first.
From our daily driving perspective, brake fluid is definitely not something you can casually substitute. I once heard at a friend's gathering that someone tried using engine oil as a replacement, and within days, the brakes failed, resulting in a crash. Brake fluid is specifically designed to withstand high temperatures and pressure. When going downhill or in stop-and-go traffic with repeated braking, temperatures get extremely high. Ordinary oils have too low a boiling point and can vaporize, causing vapor lock. Vehicle manuals clearly specify using DOT-standard fluids, like DOT 4, which has good compatibility and a high boiling point. I also learned a lesson: the brake system relies on hydraulic pressure to transmit force, and using the wrong fluid can corrode rubber components, leading to leaks. I recommend checking the fluid level monthly yourself. If you notice anything unusual, take it to a professional shop immediately—don't waste time experimenting. One wrong decision could ruin everything.
