Can engine oil be used as a substitute for brake fluid?

[LaLevi]

No, engine oil serves as a lubricant and does not have pressure, whereas brake fluid is a pressure fluid used in hydraulic braking systems. Here is the relevant information: Brake fluid: Brake fluid, also known as brake liquid or hydraulic brake fluid, is a type of fluid made from refined diesel distillate with thickeners and antioxidants. It comes in three types: mineral oil brake fluid, alcohol-based brake fluid, and synthetic brake fluid. Hazards of substitution: If engine oil is used as a substitute for brake fluid, it will result in the inability to press the brake pedal, and the engine oil will corrode the braking system, causing damage to the vehicle's braking system and severely compromising personal safety.

[SanLila]

I think brake fluid absolutely cannot be replaced with engine oil, as this is a major taboo. Brake fluid is specifically designed to transmit pressure and has an astonishingly high boiling point, typically exceeding 200°C, so it won't boil even when the brake discs glow red during emergency braking. Engine oil, however, is meant for lubricating the engine and has a boiling point of only around 100°C. If used in the brake system, it can easily vaporize under high temperatures, creating air bubbles that make the brake pedal feel spongy and ineffective, which could be fatal at high speeds. Additionally, brake fluid absorbs moisture to keep the system dry and prevent corrosion, while engine oil lacks this capability and instead allows moisture to accelerate aging. I've seen many cases where friends tried to save money by mixing engine oil for repairs, only to end up with brake failure, costly full system replacements, and near-accidents. Therefore, it's essential to use proper DOT-grade brake fluid and regularly inspect and replace it for peace of mind.

[OliveAnn]

I've been driving for over a decade, and brake fluid and engine oil are completely different things that shouldn't be mixed up. I witnessed this firsthand when I saw a villager using regular engine oil as brake fluid on a country road. When driving downhill, the brakes felt mushy like stepping on cotton—thankfully I reacted quickly and pulled the handbrake. The reason is that engine oil is too thin and can't build proper hydraulic pressure. Plus, its strong lubricating properties can damage brake seals, leading to leaks. Effective braking relies on high boiling-point brake fluid that resists failure in emergencies. I've also noticed that in humid climates, brake fluid absorbs moisture faster, lowering its boiling point, making regular changes even more crucial. Never cut corners by substituting engine oil—it won't save you money. Instead, you'll end up spending more on repairs or even compromising safety. Always follow the manual and use dedicated fluid, changing it every 2-3 years for better performance.

[DiCamila]

I've noticed many car owners think engine oil and brake fluid are both automotive oils and can be swapped to save money—this idea is extremely dangerous. In reality, brake fluid is uniquely designed to withstand high temperatures and resist moisture absorption to ensure braking efficiency, while engine oil is optimized for lubricating engines, with a lower boiling point and poor flow characteristics. Mixing it into the brake system can destabilize hydraulic pressure, causing issues ranging from inconsistent pedal feel and unreliable braking to complete brake failure and accidents. I’ve also observed that using the wrong fluid corrodes components, leading to higher repair costs—far outweighing any savings. It’s essential to use dedicated DOT 3 or 4 fluid, replaced every two years at minimal cost, to ensure driving safety instead.

[DeKhloe]

The properties of brake fluid make it incompatible with engine oil. For instance, during high-temperature braking, the temperature near the brake disc exceeds 200°C. Specialized brake fluid maintains low compressibility to ensure precise pressure transmission, whereas engine oil would already be boiling and forming bubbles at this temperature, leading to spongy brakes. I've analyzed the material differences—brake fluid additives absorb moisture to prevent internal system corrosion, a feature absent in engine oil, which instead promotes leaks. Mixing them could also clog lines or corrode rubber components, crippling brake response. Always use the correct fluid and inspect/replace it every 20,000 km to avoid risks.

[McGideon]

I believe that engine oil must never be used as a substitute for brake fluid, as it poses an unacceptably high risk of brake failure. The key difference lies in brake fluid's high boiling point and strong hygroscopic properties, which enable it to withstand the extreme heat generated during frequent braking while maintaining hydraulic system stability. Engine oil lacks these capabilities and can easily vaporize under high temperatures. My recommendation is that regular maintenance is crucial—especially in humid southern regions where brake fluid absorbs moisture rapidly, lowering its boiling point and necessitating replacement every two years. Mixing in engine oil while ignoring this fact exponentially increases safety hazards. For safe driving, always use certified DOT-grade fluids; cutting corners to save money could cost lives.