Can Other Oils Be Used as Substitutes for Motorcycle Brake Fluid?

[Santos]

No. Engine oil is much thicker than brake fluid, and their lubricating properties are different. Brake Fluid: There are three types of brake fluid. When purchasing, choose a reliable manufacturer, and the higher the grade, the better. The working pressure of the brake system is generally 2MPa, and can reach 4~5MPa in high-performance systems. All liquids have the characteristic of being incompressible. In a sealed container or a pipeline filled with liquid, when the liquid is under pressure, it quickly and uniformly transmits the pressure to all parts of the liquid. Hydraulic brakes operate based on this principle. Engine Oil: Engine oil, also known as engine lubricant, is hailed as the "blood" of a car. It serves to lubricate, clean, cool, seal, reduce friction, prevent rust, and protect against corrosion in the engine.

[MacAllie]

As a long-time motorcycle rider, I strongly emphasize safety—never substitute other oils for brake fluid. That stuff is specially designed hydraulic fluid, like DOT 4 type, with a high boiling point to withstand the extreme heat and pressure during braking. If you use engine oil or transmission fluid instead, their lower boiling points will cause them to vaporize under high temperatures, forming bubbles and making the brakes completely fail—like stepping on cotton, all mushy. I once heard a tragic story at a riders' meetup where someone cheaped out and used household engine oil, leading to brake failure while descending a hill, resulting in serious injuries. Even worse, the wrong oil can cause system corrosion or swelling of rubber seals, making repairs far more expensive. I recommend checking fluid levels during every service and only using the manufacturer-recommended specifications—don’t gamble with your life to save a few bucks. Regular replacement is also crucial, typically every two years, to keep the brakes responsive.

[McAxel]

Having worked in the motorcycle repair industry for many years, I've seen too many people messing around with the brake system, leading to disastrous consequences. Brake fluid must never be replaced with other liquids, such as engine oil or coolant—these random substitutes have completely different chemical properties. Brake fluid has strong hygroscopic properties, preventing internal corrosion and boiling. If replaced with other oils, the boiling point drops sharply, causing bubbles to form during high-temperature braking, resulting in an instant loss of hydraulic pressure and the vehicle being unable to stop. In real cases, I've handled several accident vehicles where the entire brake system was ruined after using non-specialized fluids, requiring full component replacements and doubling repair costs. Always use the specified DOT grade, such as the model recommended in the vehicle manual. During routine maintenance, I also remind customers to check if the fluid reservoir is dirty or leaking to ensure hydraulic efficiency. Don’t cut corners—safety comes first.

[ReeseMarie]

When I first started riding, I made a silly mistake by thinking I could use car engine oil as a temporary substitute for brake fluid. That trip turned out to be a disaster—the brakes were sluggish and made awful squealing noises, nearly causing a rear-end collision. The painful lesson: brake fluid is a specialized hydraulic medium. Other oils have too low a boiling point, forming air bubbles under high temperatures and losing braking power. At the repair shop, the mechanic told me the entire system was almost rusted through, costing me hundreds to clean and replace. Now, I only use genuine brake fluid and check its condition regularly. Simple maintenance can save lives.