Red Is the Color You Want Your Transmission Fluid to Be

It might seem strange, but the color of your transmission fluid is very important. As your transmission fluid ages, it changes color. This helps auto technicians determine when the transmission fluid needs to be changed, although the general rule of thumb is every 30,000 miles. Hummel’s Automotive & Diagnostic Repair would be happy to check your transmission fluid if it has been a long time since you’ve had it flushed and refilled. We are going to list the different stages of transmission fluid life below by color.


You want your transmission fluid to be bright red. Bright red and translucent transmission fluid is in perfect condition. The transmission fluid is both a hydraulic fluid and a lubricant. In other words, this fluid helps your transmission shift gears and also protects it. When the transmission fluid is red and, again, translucent, it is doing its job without fail. You do not need to change red and translucent transmission fluid.


Transmission fluid goes through many stages of browns as it begins to age. The first stage is light brown. This fluid remains translucent and darkens slightly so that the hue appears browner than red. In some cases, the fluid may also look orange. As long as the fluid is light brown and translucent, it’s still helping the transmission shift gears and protecting it. You can wait a while until you have the fluid changed.

Once the fluid turns brown, it needs to be changed. The reason why the transmission fluid is changing from bright red to brown is that it is oxidizing. As the fluid oxidizes, it becomes less effective in helping the transmission shift gears. Also, because the fluid is filling with air bubbles, it doesn’t do as good a job of protecting the transmission from heat, wear, and tear.

As we just mentioned, brown transmission fluid needs to be changed. If your transmission fluid is black, you are likely experiencing transmission problems. These problems can include difficulty shifting gears, a lack of engagement when you put the transmission into gear, and grinding or squealing as the vehicle shifts gears.


As an aside, in rare cases, there can be a breach between the transmission and the cooling system that causes coolant to mix with transmission fluid. If this happens, your transmission fluid will turn pink and become frothy like a milkshake.

Again, Hummel’s Automotive & Diagnostic Repair in St. George, UT, would be happy to check your transmission fluid. Give us a call today to schedule an appointment.

Photo by chat9780 from Getty Images via Canva Pro

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