When should you change your brake fluid?

Les McMaster

Some manufacturers, he said, still recommend changing brake fluid every two years; some have moved to three- or five-year intervals and others have removed the recommendation for periodic flushing and refilling from their maintenance schedules.

Brake fluid transfers force fluid to the various components of the braking system when the brake pedal is depressed, "so customers are right to be concerned about proper maintenance", said McMaster.

Traditionally, brake fluids have been glycol-based DOT 3 and DOT 4. Over time, these fluids absorb moisture from the atmosphere, which reduces their boiling point and, therefore, effectiveness; however a water-repelling silicone DOT 5 brake fluid has gained popularity over the past few years.

McMaster explains that the silicone in this brake fluid doesn't absorb moisture as quickly, removing the main reason for doing brake fluid flushes in the past. Attracting more moisture and boiling at higher temperatures on braking is the cause of brake failure. "With silicone, the moisture intake is reduced, it doesn't boil as fast, there is less corrosion in the system, and it has a longer life."

Stick with your manufacturer's prescription

He offers a word of warning, however, saying brake fluid types aren't easily interchangeable: "You'll need to stick with your manufacturer's prescription.

"It's not like the old days where one brake fluid, or one transmission fluid, worked in all makes and models. There are so many now that you have to be aware of, and different manufacturers have different recommendations," said McMaster, who recommends a brake fluid change every six years or 80,000 kilometres. "Silicone-based brake fluid is becoming more predominant on all the newer cars, but six or seven years ago it would only show up in the BMWs, Mercedes, Lexus and high-end cars. With an ABS braking system, some manufacturers use silicone brake fluid, and some don't. It really is specific to the manufacturer."

It may be that a new vehicle requires a silicone-based fluid and, therefore, has a reduced requirement for flushing and refilling. Some manufacturers of glycol-based fluids also claim that special additives in their products make them lifetime fluids. In addition, some auto makers say the features of their modern brake systems make them comfortable with reduced flush and refill recommendations. "If you plan to hang onto the car once it's out of warranty, you'll to want to keep the braking components in tip-top shape."

Given the high cost of certain brake components, the peace of mind gained through this relatively inexpensive procedure makes it worthwhile.

"It's important to note that this is not a do-it-yourself procedure. The extremely high pressures generated by modern anti-lock brake systems can put you at great risk of injury if you fail to follow the servicing procedure to the letter. Rather contact your manufacturer or visit your nearest MIWA service centre for further clarification on when to change your brake fluid. If in doubt, stop at any MIWA brake or repair shop, where they can determine if the fluid requires changing with a simple litmus test," he concluded.