To ensure you receive the best service possible,
please enter your zip code below:
When you go through a long, hot day without drinking water, your energy levels plummet, your muscles seize and cramp and your mental gears start slipping until, eventually, your body refuses to cooperate. The same concept is true for your vehicle. Like you, your vehicle requires a variety of fluids to perform properly. When they run low or become contaminated or your car gets dehydrated, it becomes less efficient and can break down much like you would if you were deprived of water.
Seven vital fluids help your vehicle stay healthy and functional. Below, find out what these fluids are, what they do, and why they are important to your vehicle's health and operation.
What engine oil does: Engine oil lubricates moving parts, reduces friction between metal parts, minimizes wear, and disperses heat. It also prevents carbon buildup, dust and metal shavings from clogging internal components. Some oils can even clean the engine as they flow into every part of the engine.
Why it’s important: When an engine is deprived of oil, it can suffer from heat exhaustion (overheat) and seize up. Additionally, oil prevents metal components like pistons, crankshafts and camshafts from grinding, warping and cracking, which could result in total engine failure.
Top consideration: Synthetic oil is more expensive than traditional motor oil but performs an average of 47% better than conventional oil. Among the advantages of synthetic oil are better low- and high-temperature viscosity performance, increased stability and less initial drag on the engine for improved horsepower and torque.
Eco-friendly alternatives: Though not as common, bio-based oil alternatives exist. These oils are made from canola or esterified plant oils and are less toxic and biodegradable. They are most often used in agricultural environments or where an oil leak could contaminate waterways or soil. Check your vehicle manufacturer’s recommendations before switching to one of these eco-alternatives.
What it does: Transmission fluid is a multi-purpose lubricant that helps prevent heat and friction damage to the clutch, bearings and valves. It also provides the necessary hydraulic pressure for gear shifting. This allows for smooth and efficient transitions between the gears. Lastly, this fluid preserves the pliability of your transmission’s seals and gaskets.
Why it’s important: A transmission failure is one of the costliest repairs you could incur as a vehicle owner. Without the fluid to keep it cool and prevent grinding, seizing and overheating, your vehicle will experience sluggish shifting, gear slips, rough gear engagement and eventually complete failure.
Top consideration: Your transmission fluid doesn’t need to be changed often. Depending on your vehicle’s typical driving conditions, transmission fluid can last 100,000 miles or more. But it’s certainly less expensive to replace the fluid than your entire transmission, so get the level checked.
Eco-friendly alternatives: While less common than biodegradable engine oils, green transmission fluids are available. Renewable Lubricants produces bio-based transmission fluids that meet or exceed performance specs for some machinery and commercial applications. Though these greatly reduce the environmental impact of spills and leaks, they are not yet compatible with all passenger vehicles. Consult your owner’s manual or mechanic before making the switch.
What it does: Brake fluid is the specialized hydraulic fluid needed to operate one of your vehicle’s most essential functions – brakes. Every time you press the brake pedal, this fluid is transferred through pressurized lines to engage the brake calipers and wheel cylinders. When these components are engaged, they press your vehicle’s brake pads or shoes against the rotors or drums, applying the necessary friction to slow the car. Modern brake fluids protect metal surfaces from corrosion and prevent rubber seals from drying out.
Why it’s important: Over time, brake fluid chemically degrades as it naturally absorbs moisture from the air. This degradation leads to a spongy pedal (a brake pedal that feels soft or lacks firm resistance) or total failure. If the fluid is low or too much air gets into the brake line, you may be unable to stop your vehicle properly. To prevent this, it is important to periodically change your brake fluid out, even if it looks fine.
Top consideration: If the brake fluid level is low, there is likely either a leak or some other serious problem in the brake system. Have a qualified technician inspect the brakes right away.
Eco-friendly alternatives: Biodegradable alternatives are extremely rare in the consumer market due to the extreme performance demands of braking systems. Some non-toxic fluids are available for agricultural and forestry applications but have not yet entered the mass vehicle market.
What it does: This fluid powers the steering gear and makes steering easy. This hydraulic fluid transmits power within the power steering system by transferring movement from the steering wheel into motion at the wheels. This makes vehicles easier to steer and operate, especially at low speeds or dead stops. Additionally, this fluid acts as a lubricant for the steering pump and gear, reducing friction between moving parts and preserving rubber seals and hoses. It also helps protect seals and rubber hoses in the system.
Why it’s important: Dirty or low fluid could cause the steering system to lose pressure which leads to steering that is sluggish, jerky or rigid. In extreme cases, the steering pump could overheat and fail. It is important to change the fluid occasionally, even if your vehicle’s steering system feels fine, because neglect will shorten the system's lifespan.
Top consideration: A buzzing noise when the steering wheel is turned at low speeds can indicate low power steering fluid.
Eco-friendly alternatives: Green alternatives do exist for agricultural and industrial equipment, but they are rare for consumer street vehicles. Synthetic fluids, while not green, reduce maintenance frequency and lower the risk of leaks, making them an environmentally responsible choice for your vehicle.
What it does: Coolant is essential for the temperature regulation of your vehicle. This specially formulated fluid absorbs heat from your vehicle’s engine and carries it to the radiator, where it is dispersed into the air. Coolant keeps the engine from freezing up in frigid temperatures by lowering the freezing point of the fluid in your engine block. During the summer, it raises the boiling point, which helps prevent overheating. Outside of temperature control, this fluid lubricates the water pump seals and protects the cooling system from rust and corrosion.
Why it’s important: Your engine operates at extremely high temperatures. If they are not regulated, your engine could overheat, cylinder heads could warp, head gaskets could blow and in extreme cases, the engine block could crack. If that happens, the repair could cost you thousands. Old or diluted coolants are not as effective when protecting your vehicle. Changing your coolant periodically is essential for maintaining your vehicle’s engine health.
Top consideration: Get your coolant tested at least once a year, preferably before the onset of winter in colder regions, to determine its level of antifreeze protection.
Eco-friendly alternatives: While most coolants are made of ethylene glycol which is harmful to humans and animals alike, there are propylene glycol-based alternatives that are “low-tox” or “pet-safe.” These alternatives break down more easily in the environment and offer reduced environmental risks in the event of a spill. Though these are safer than their ethylene counterparts, large quantities are still hazardous to people and animals.
What it does: Washer fluid is often a specially formulated liquid that is expelled from your vehicle’s washer nozzles to clear bugs, dirt, bird poop, grime and other windshield stains. It works in tandem with your wipers to maintain visibility. Most of these fluids are a mixture of cleaning agents, water-repellents, bug dissolvers and antifreeze chemicals to prevent streaking, freezing and debris buildup.
Why it’s important: A dirty windshield compromises your ability to see the road, traffic signs, people or other vehicles. Dirty, smeared windshields are most hazardous during low-light conditions when glare from the sun or headlights amplifies the dirt buildup. A clear windshield is essential for the safe operation of your vehicle. That is why you must ensure your washer fluid is regularly topped off.
Top consideration: In colder areas, use a fluid formulation that won’t freeze on your windshield.
Eco-friendly alternatives: Nextzett, ECOS and Prestone Bio offer environmentally safe washer fluid alternatives. They use bio-based surfactants and remove methanol, a common toxic alcohol found in most washer fluids, altogether. Look for “green” or “non-toxic” labels if you would like to explore these options.
What it does: Fuel is a vital part of your vehicle's combustion process. When fuel is injected into the engine’s cylinders, it is mixed with air, compressed and ignited creating a controlled explosion that sets the pistons and crankshaft into motion to create the force needed to move your vehicle. In modern cars, fuel also cools injectors, lubricates components and helps maintain the emissions system.
Why it’s important: Check your vehicle owner’s manual to determine which gasoline or diesel fuel type is recommended or required. Using the proper grade of fuel can have a significant impact on your vehicle’s performance and reliability. Using a lower grade than required could reduce power, lead to poor fuel economy and excess wear. Using gas in a diesel vehicle could ruin your engine. The wrong fuel could cause clogged injectors, damaged fuel pumps, trigger check engine lights or, in extreme cases, lead to total engine failure.
Eco-friendly alternatives: Several options are available for a green alternative to your vehicle’s fuel needs. Ethanol blends, biodiesels and renewable diesels burn cleaner and reduce carbon emissions. There are also electric and hybrid options, which take bigger strides to reduce fossil fuels. Be sure to refer to your owner’s manual or consult your mechanic before choosing one of these alternatives, as not every vehicle is designed to use them.
Top consideration: AAA Members save at least 5¢ per gallon at participating Shell stations when joining the Fuel Rewards® program. Restrictions apply.
When you go the DIY route, remember that AAA Members save 10% and earn NAPA Rewards points on most auto parts and accessories at NAPA.
Q1: How often should I check my car’s fluids?
A: Check your car’s essential fluids—like engine oil, coolant and brake fluid—at least once a month or before long road trips. Always refer to your vehicle owner's manual for specific recommendations.
Q2: What are the signs of low or contaminated car fluids?
A: Warning signs include dashboard warning lights, unusual engine sounds, sluggish gear shifts, spongy brakes or a dirty windshield. Regularly checking fluid levels can help you spot problems early.
Q3: Can I check car fluids at home myself?
A: Yes! With basic tools and safety steps, you can check engine oil, coolant, brake fluid, windshield washer fluid and power steering fluid at home. Park on level ground and use clean techniques to avoid contamination.
Q4: Are there eco-friendly alternatives to traditional car fluids?
A: Yes. Bio-based oils, propylene glycol coolants and non-toxic windshield washer fluids offer greener options. Always check your owner’s manual or consult a mechanic before switching.
Caring for your vehicle
AAA can help you keep your car running at peak performance. AAA Members receive a free vehicle maintenance inspection upon request with any paid service at a nearby AAA-owned Car Care center or AAA Approved Auto Repair facility, a 36-month/36,000-mile guarantee on repairs at AAA-owned Car Care locations, and a 24-month/24,000-mile warranty at AAA Approved Auto Repair facilities. Members also receive a 10% discount on repair labor (save up to $75).
