Car hydraulic fluid

Change intervals for hydraulic fluids

There are several systems in your car that are based on hydraulic technology. In your typical car or truck, the main three systems are your automatic transmission, your brake system and your power steering system. Since all three of these are sealed systems, the fluids don’t get dirty very quickly, but that doesn’t mean that they don’t lose their effectiveness. Hydraulic fluids are usually loaded with special components to lubricate, absorb water and prevent corrosion. Unfortunately, these components lose their effectiveness over time. In this article, we will look at the manufacturer’s recommended change intervals for these three common systems.

Automatic Transmission Fluid
Automatic transmissions are remarkably complex, hydraulic devices. They have bands, seals, gears and shuttle valves that all “run” on hydraulic fluid. After a certain amount of use, this fluid, usually called Automotive Transmission Fluid (ATF), wears out and needs to be changed. The suggested change interval for most transmissions these days is 60,000-100,000 miles. In the past, some manufacturers suggested that the fluid would be replaced only when a “change in transmission shifting occurred.” In other words, when the transmission just didn’t shift as well as it did when new. Today, however, automatic transmissions are “smarter” and can mask worn and depleted transmission fluid by adjusting shift points automatically. The solution is to change the fluid when recommended, and your mechanic may recommend a “transmission flush” too.

Power Steering Fluid
The suggested change interval for today’s power steering fluids is 60,000-80,000 miles. Not long ago, there was no definitive change interval for power steering fluid because it really didn’t get dirty and worn out but things are different today. Wider wheel and tire packages are putting more strain on power steering systems and this means more heat is generated. If it gets hot enough, the heat can degrade the fluid and eventually damage the seals in the pump and rack. Hence, most manufacturers now have recommended change intervals for their power steering fluids.. Unlike transmissions, there is no real way to flush a power steering system but a good fluid change at the manufacturer’s suggested mileage will keep things running well.

Brake Fluid
The suggested change interval for today’s brake fluids varies from every 100,000 miles to 150,000 miles. The specific time depends on the manufacturer. Some old timers will find this odd because in the old days, brake fluid was rarely changed. Today, systems like ABS have become standard on most vehicles and these can be hard on a car’s brake fluid and it will wear out.

A note for do it yourselfers
Our subject matter experts for this article, Central Ave. Autogroup in Yonkers, NY, remind us that there’s an old saying: “There is no such thing as a universal fluid.” Different manufacturers use different formulations for their power steering, transmission and brake systems that are matched to the type of seals they have installed in the system. If you add the wrong fluid to your car’s automatic transmission, for example, you may end up ruining the transmission seals. So, make sure that before you add any fluids to your car, check your driver’s manual for the correct fluid type, or with your local brand dealer for their recommendation. Don’t wing it.