Transmission Fluid 101: When and Why to Change It

Transmission fluid does more than lubricate — it cools internal components, transfers hydraulic pressure, and keeps seals conditioned. When it breaks down or runs low, everything downstream suffers. Here’s what our specialists tell customers about keeping fluid in good shape.

What Transmission Fluid Actually Does

In an automatic transmission, fluid is the medium that transfers power through the torque converter and operates the hydraulic systems that control shifting. It also carries heat away from internal components. When fluid degrades, it loses its ability to do all three.

How Often Should It Be Changed?

As a general guideline, automatic transmission fluid should be checked regularly and changed roughly every 40,000 km or every two years — whichever comes first — under normal driving conditions. If you tow, haul heavy loads, or drive a diesel, shorter intervals are usually a good idea; see our towing and diesel transmission care guide for specifics. Always confirm the interval for your specific vehicle, since it varies by make and model.

Signs Your Fluid Needs Attention

• Colour: Healthy fluid is typically red or brown; dark, cloudy, or burnt-smelling fluid needs attention.
• Level: Low fluid can point to a leak, which should be found and fixed, not just topped up.
• Smell: A burnt odour usually means the fluid has overheated and broken down.

For the full list of related symptoms, see our guide to transmission warning signs.

Use the Right Fluid Type

Not all transmission fluids are interchangeable. Using the wrong type — especially in a CVT — can cause more harm than skipping a service altogether. Always use what’s specified for your vehicle, or ask us to confirm before any fluid service.

Book a Fluid Service

A fluid check takes minutes and can catch problems long before they become expensive ones. Visit our Woodstock shop, our head office and largest service centre, or Brantford or Simcoe if that’s closer, or contact us to book. More preventive guidance is available on our Transmission Tips hub.