What Fluids in a Car Need to be Changed?

Cars need a lot of fluids. Sure there’s stuff like gas or diesel that the engine converts to energy, but that doesn’t begin to scratch the surface. Braking, steering, engine cooling systems, the transmission, and more require fluids to work properly. Learn about the different fluids you need to change to keep your ride running smoothly. We’ll include an estimate for when each fluid needs to be changed, but the actual amount of time depends on what you drive, so check your owner’s manual for the most accurate information.

Car Fluids You Need to Change


Motor Oil

When your engine is in operation, a lot of metal parts rub against each other. This rubbing would generate a lot of friction and heat without oil to lubricate the engine’s internals. Traditional wisdom puts the oil change interval every 3 months or 3,000 miles, but this interval will differ depending on your year, make, model, and engine, as well as the type of oil you use (conventional or synthetic). Check your owner’s manual for the correct interval.


Transmission Fluid

This fluid lubricates the gears in your transmission fluid to help it run effectively. You don’t need to change transmission fluid nearly as often as oil. It will generally last 50,000, 100,000, or 150,000 miles, but once again the best way to know the correct service interval is by consulting your owner’s manual.


Brake Fluid

Most braking systems use hydraulic fluid and a combination of master and slave cylinders to compress calipers to squeeze the pads to the rotors and bring the vehicle to the stop. Brake fluid generally should be flushed when the pads and rotors are replaced.


Engine Coolant

Engine coolant, or antifreeze, does what it sounds like it would do: it cools your engine. Without it, the engine would overheat and break. When you need new coolant depends on what your drive, so check that owner’s manual.


Power Steering Fluid

Hydraulic power steering systems use hydraulic fluid similarly to how brake fluid works. Generally it should be changed every two years or 50,000 miles.


AC Refrigerant

R-134a is an automotive air conditioning refrigerant, meaning it’s the fluid that lets your car’s AC keep the interior cool. If your AC is blowing hot air, it’s wise to grab a refill kit so you can keep cool.


Windshield Washer Fluid

Washer fluid isn’t a crucial maintenance fluid in that your car can still function without it. That said, you’ll regret not topping it up if something gets on your windshield while you’re driving. There are special formulations for removing bugs or ice and frost as well as general purpose fluids. There’s no precise interval for replacing this fluid, but you can check it under the hood and fill up as needed.

Helpful How-To’s

If it’s time to change any of your car’s fluids, shop online or go to your local AutoZone to find any fluids your vehicle needs. Our associates can help you find out which fluids need to be changed and which versions of the fluid to use for your specific vehicle.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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