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Technical Tips

When to Change Brake Fluid

Break out the calendar

From oil changes to filter replacements, many routine car maintenance jobs are performed on a schedule based on miles traveled and/or time intervals. While some car companies and brake fluid manufacturers continue to suggest a set amount of miles between brake fluid changes, Wagner® doesn’t subscribe to a mile-based recommendation. Read on to learn why changing Wagner brake fluid based on years elapsed is the best way to ensure its effectiveness.

Laying out the issue


Most brake fluid used in today’s vehicles is glycol-ether based (DOT 3, 4 and 5.1), while some vintage vehicles use silicone-based DOT 5 brake fluid. Brake fluid that is in good condition is critical to the overall health and performance of a vehicle’s brake system; for example, water and copper are the enemies of brake fluid. Over time, brake fluid can also absorb moisture which can lead to corrosion in the brake lines and brake system, as well as lower the boiling point of brake fluid, reducing the effectiveness of the brake pedal. 

The presence of copper is a good indicator of the condition of brake fluid. When brake fluid deteriorates, copper levels rise, signaling that the fluid is losing its effectiveness. As brake fluid breaks down (high copper levels), the brake fluid no longer has adequate anticorrosive inhibitors so corrosion of internal brake hydraulic components may occur. To avoid breakdown, Wagner recommends that brake fluid should be changed when the copper content is 200ppm (parts per million) or more


Wagner’s change recommendations depend on which type of brake fluid you are working with. If no OEM recommendation is given, Wagner makes the following suggestions (please note that these intervals could be shorter in humid climates): 


For heavy-duty trucks or vehicles that tow or are under severe stress, you may want to test the brake fluid to ensure that it is up to peak performance.


  • Wagner DOT 3 & 4 brake fluid is a convenient option for those who need both DOT 3 and DOT 4 brake fluids.

  • DOT 3, 3 & 4 and 5.1 are all glycol-based brake fluids that are compatible with each other and can be mixed without having harmful effects on a vehicle’s braking system.

  • It is important never to mix or mistake DOT 5.1 (glycol based) with DOT 5, which is silicone based. DOT 5 can never be mixed with any other DOT fluid but DOT 5.

Learn more about quality brake parts, find your car part, or find where to buy your auto part today. 

The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.

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