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A Guide To Your Car’s Fluids

what car fluids need to be changedSpringtime in Arizona is the perfect time to go for a long drive. You can head north and marvel at the Grand Canyon or drive across town to attend one of the many spring festivals. Just make sure before you hit the road, the fluids in your car are in good condition and topped off to ensure your trip is a smooth one. After all, the fluids in your car are the key to keeping major components working seamlessly. Fluids help to keep parts lubricated, cooled, and conditioned. Though each fluid is designed to perform a different task, they are all of equal importance. Most every driver knows that the oil must be changed every 3,000 to 5,000 miles. But if you’re only changing your oil and neglecting to replace other fluids, you’re doing yourself and your car a disservice. Learn about the six major fluids in your car and how they work to keep your car going for miles and miles. 

Engine Oil

Motor oil is the most vital fluid in combustion engines. Engine oil comes in several forms including conventional, synthetic blend, full synthetic and others. Conventional oil is a petrol-based oil made from crude oil found underground. Full synthetic oil is a crude oil that has been purified and enhanced with synthetic additives making them more resistant to heat and sludge build up. Synthetic blend oil is the happy medium between conventional and full synthetic oils containing a combination of both. Oil not only lubricates moving parts in the crankcase, it also helps cool engine components from the high heat and friction produced during operation. Friction can damage pistons, valves, and other essential components. An engine that is operating without oil won’t last long and can cause long-term damage. 

When to replace: Depending on the kind of oil your vehicle requires, change every 3,000 – 5,000 miles. Refer to your owner’s manual to determine what oil is best suited for your car.

Transmission Fluid

Transmission fluid is the key to ensuring your transmission continues sending power to the wheels and smoothly shifting from gear to gear without hesitation. In addition to helping shift gears, transmission fluid helps lubricate moving parts, reduce heat created by friction, keep the transmission cool during operation, and conditions gaskets and other components to increase efficiency. Transmission fluid is often bright red in color but can darken from deeper shades of red to brown and even black based on the transmission’s condition.    

When to replace: Have a transmission flush performed every 45,000 miles or every three years. 


 Coolant is a heat transfer fluid made up of a mix of water and chemicals, however, the ratio of water to coolant can vary based on climate. The coolant’s job is to keep the engine cooling system lubricated and cool and protect from freezing. Coolant/water travels throughout the vehicle’s engine collecting heat and returns to the radiator where heat is dissipated into the air, and then, the cycle begins again. Little to no coolant/water in the engine is often a result of a leak in the system and can quickly spell disaster. A vehicle without the proper level of coolant is at risk for overheating. Allowing an engine to overheat can cause extensive damage to the engine that may lead to costly repairs or replacement.

When to replace: A coolant flush should be performed every 30,000 – 50,000 miles.


Also known as Freon/R12, 134a, and now 1234YF, car air conditioner fluid/refrigerant is responsible for making the air that comes out of your vents cold. Refrigerant begins in a liquid state and is compressed into a gaseous state to regulate the temperature of your car inside. The air conditioning system is a pressurized system, and should the system develop a leak, the refrigerant may leak out and evaporate. Components in the air conditioning system will not be able to function without refrigerant.

When to replace: Fluid should only be replaced by a qualified technician, in the event of a leak, after an evacuation and recharge has been performed or after any service has been performed on the air conditioning system.  

Power Steering Fluid

Power steering fluid is pressurized by a hydraulic pump driven by the engine, making turning the vehicle a simpler process. Power steering fluid keeps steering components well lubricated and protected from failure. Due to the significant pressure needed for turning, much heat is generated during the process and can cause the fluid to breakdown. Unlike many other areas of the vehicle, power steering systems lack filtration and over time, the fluid becomes contaminated and can cause power steering components to deteriorate. 

When to replace: A power steering flush should be performed every 30,000 miles. By having this service performed, you’re ensuring the power steering pump is protected from overheating and protecting other steering components.

Brake Fluid 

Your car’s brake fluid, as part of the brake system, is considered a safety feature of the vehicle and is vital to your safety as well as others. The brake system is a highly pressurized hydraulic system that is used to increase the vehicle’s ability to stop. When the driver presses down on the brake pedal, which is connected to the brake master cylinder the fluid is pushed to pistons in the brake caliper at each wheel. This process greatly increases the pressure which sends the fluid into motion, signaling the brake pads to compress against the rotors that are in contact with the wheel, to stop their rotation. A significant reduction in brake fluid is concerning and could put your safety at risk. Do not drive with low brake fluid. 

When to replace: Flush the brake fluid every 30,000 miles or any time you have a brake service performed. A brake flush removes any bits of debris, moisture, and dirt from the system ensuring your braking experience is a smooth one.

Windshield Washer Fluid

Though not as vital as some of the other fluids above, wiper fluid is a soapy blend that keeps the windshield clear of any dirt, smudges, and other unpleasant particles while you drive. In addition to keeping your windshield dirt and bug-remains free, the washer fluid acts as a lubricant for the washer fluid pump, hoses, and spray nozzles. Without fluid, internal components may corrode and wear out. Likewise, if the washer fluid pump cannot pump any fluid or the rubber hoses dry out and crack from the inside, the entire system may be compromised. Attempting to use the washer fluid pump without fluid in the reservoir places strain on the pump and may cause it to wear out prematurely. 

When to replace: Fill up every 3,000 – 5,000 miles. Ideally, your automotive service provider should top off this fluid for you every time you have an oil change performed.

You don’t need to wait for your next automotive service to have fluids checked in your car. Most vehicles provide dipsticks for you to check oil, coolant, brake, power steering, washer, and sometimes transmission fluid. If you notice any kind of fluid on the ground, it’s possible you may have a leak, but determining what component is responsible may be difficult. Refer to this car fluid color guide to help clue you in on what may need attention and then, bring your vehicle to Sun Devil Auto for superior auto care.