Car fluids are the hidden heroes that keep your engine running smoothly. Without fluids like engine oil and brake fluid, your rides would become uncomfortable and unsafe.
Let’s explore the nine fluids to check in a car and how to verify their levels. We’ll also discuss when to change them and tell you ways to identify different fluids if there’s a leak.
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9 Common Fluids to Check in Car (+ How to Do It)
Your car has nine important fluids that must be monitored and refilled on time. But, since they’re located in different parts of the vehicle, it can be difficult to monitor their levels yourself. Also, many of these fluids are toxic, so it’s best to get them checked by an auto repair mechanic.
Here’s a look at the essential fluids a mechanic will check in your car and how they’ll do it:
1. Engine Oil
Typically yellow or amber in color, engine oil is a vital fluid that lubricates parts under the hood. Without proper lubrication, engine components can experience friction, which leads to car overheating.
Maintaining sufficient engine oil level is necessary to ensure a smooth vehicle operation.
How to check the car’s oil:
- The mechanic will refer to your owner’s manual for locating the dipstick (usually has a yellow handle and an oil can symbol).
- Then, they’ll remove the oil dipstick from the tube connected to the crankcase (oil reservoir) and wipe off any existing fluid.
- Next, they’ll reinsert the oil dipstick into the tube and pull it out to check the level.
- They’ll check if the engine oil level is near the “Maximum” line. If it’s not, they’ll add fresh oil to the reservoir.
NOTE: With time, your car’s oil can become contaminated and dark. Black or brown motor oil indicates it’s time for an oil change.
2. Brake Fluid
This important fluid assists the brake system in stopping the vehicle when needed. A new and clean brake fluid is usually clear, yellow, or amber in color.
When the fluid level is low, your brake pedal will feel soft, and you may struggle to control your car’s speed. To avoid accidents, get your brake fluid checked regularly alongside other car care services.
How to check the brake fluid level:
- The mechanic will open the car hood and locate the semi-translucent brake fluid reservoir attached to the master cylinder.
- Next, they’ll look for the reservoir’s “Maximum” and “Minimum” markings and verify the fluid level.
- If there’s low brake fluid, they’ll add fresh liquid to the reservoir.
3. Automatic Transmission Fluid
Transmission fluid is an amber or red hydraulic fluid that lubricates essential moving components of the transmission, such as gears, clutches, and valves. In modern cars with an automatic transmission, the fluid also helps create hydraulic pressure.
However, less fluid makes the transmission prone to stiff shifting, surging, and seizing.
How to check the automatic transmission fluid’s level:
- The mechanic will start your car to keep the engine running and engage the parking brake.
- Then, they’ll locate the transmission fluid dipstick.
- Next, the mechanic will insert and remove the dipstick from its tube to inspect the level.
- If the fluid level is low, they’ll top it off with a fresh batch, but if it’s dirty, they’ll perform a flush.
4. Power Steering Fluid
This pinkish hydraulic fluid is used within the steering system. It acts as a bridge between the steering wheel and the car’s wheels. It reduces the effort needed to turn the wheels and lubricates power steering system parts. But if the steering wheel feels stiff to turn, it indicates a low fluid level.
How to check the power steering fluid level:
- The mechanic will turn on the engine and let it idle for 3-4 minutes to heat the steering fluid.
- Next, they’ll locate the reservoir cap.
- They’ll check whether the fluid level is between the “Maximum” and “Minimum” indicators and top it off if it’s low.
5. Radiator Fluid (Coolant or Antifreeze)
The coolant fluid can be green, blue, yellow, purple, or pink in color. This liquid absorbs heat to maintain the engine’s temperature and prevent rust and corrosion. However, issues like a leak can lower the coolant fluid level, requiring immediate attention.
How to check the coolant level:
- The mechanic will turn off the car and wait for it to cool down, as the engine coolant can be extremely hot.
- Then, they’ll locate the reservoir cap labeled “radiator fluid” or “antifreeze” on the top of your radiator.
- After removing the radiator cap, they’ll observe whether the coolant reservoir is filled to the top. If not, they’ll top it off.
6. Windshield Washer Fluid
The white or blue-colored windshield washer fluid removes debris and dirt marks from the windshield to keep your view unobstructed when you drive. But, if you often drive on dusty roads or during rain, it’s best to monitor its level frequently.
How to check windshield wiper fluid level:
- Your mechanic will open your car’s hood and locate the washer fluid reservoir.
- Next, they’ll remove the cap and visually inspect the fluid level (which should be near the “full” mark).
- If the fluid level is low, they’ll top it up.
NOTE: Many modern cars have a rear wiper, which could have a separate reservoir. If so, the mechanic will refill the rear wiper’s fluid as well.
7. AC Refrigerant
Refrigerant is a colorless substance that absorbs heat and works with the AC system parts to push cool air through the vents. Without ample refrigerant in the air conditioning system, your car vents will blow warm air.
How to check refrigerant level:
- The mechanic will locate the high-pressure service port near the air conditioning compressor to perform the fluid check.
- Then, they’ll connect the refrigerant gauge to get an accurate reading.
- The low-pressure port reading should be between 25 and 45 psi (pounds per square inch), while the high-pressure port should be between 250 and 400 psi.
- They’ll add more refrigerant if the readings aren’t within the recommended range.
8. Differential Fluid
This vital fluid lubricates differential system parts like the pinion gears and bearings. It’s also called gear oil and is amber or dark brown in color. If there’s insufficient fluid, the differential can fail, putting you in danger.
How to check the differential fluid level:
- The mechanic will refer to the owner’s manual to locate the differential’s fill plug.
- Then, they’ll use a ratchet to release the plug.
- Ideally, the fluid should spill out when the plug is removed, but it won’t if your car is low on differential fluid and needs a refill.
9. Transfer Case Fluid
All-wheel and four-wheel drive cars have a transfer case or unit that contains a lubricating fluid.
The transfer case fluid is a blue, brown, green, or yellow liquid that lubricates and cools the internal parts of the case. But if dirt or contaminants enter the fluid, it’ll fail to perform its functions.
How to check the transfer case fluid:
- The mechanic will locate the transfer case beneath the vehicle.
- Then, they’ll find the fill plug located on the transfer case’s side.
- Next, they’ll check if the fluid is at level with the bottom of the fill plug hole.
- If the fluid level is low, they’ll refill it, but if it’s contaminated, they’ll replace it.
Now that we’ve covered the essential fluids you should check in your car, let’s go over some common questions asked about them.
4 FAQs about Car Fluids
Here’s some additional information about car fluids that you’ll find useful:
1. What Is the Purpose of Fluids in Your Car?
Vehicle fluids, from coolant to engine oil, are crucial for maintaining the longevity of different car systems.
Without these fluids, your engine components, transmission system, and differential will deteriorate and eventually fail completely. Ignoring them for too long can also lead to expensive repairs.
2. What Happens If You Drive with Low Car Fluid Levels?
Driving with low (or no) vehicle fluids can put you, your passengers, and other drivers in grave danger and should be avoided at all costs.
For example, if your car’s running on low brake fluid, the braking system will eventually fail. Similarly, less steering fluid will strain the power steering system to turn your vehicle. In both situations, you won’t have complete control over your car, which can put you at risk of an accident.
So, check your car’s fluids regularly and never skip a vehicle maintenance service.
3. How Often Should You Change the Car Fluids?
The recommended change intervals for your car’s fluids may differ for each liquid. However, here’s a rough guideline you can follow:
- Windshield washer fluid should be refilled during every car maintenance service, season change, or whenever it runs out.
- Refrigerant usually lasts for the vehicle’s lifetime but may require a refill if the AC system is faulty or leaking.
- Engine oil can usually go 5,000 to 10,000 miles between changes, with some manufacturers recommending up to 15,000 miles.
- Brake fluid should be changed at least every 30,000 miles.
- Radiator coolant, differential, and transfer case fluid should be refilled every 30,000 to 60,000 miles.
- Power steering fluid should be replaced every 40,000 to 80,000 miles.
- Automatic transmission fluid can go 60,000 to 100,000 miles before needing a change.
4. What Should You Do If You Notice a Fluid Leak or Fluid Loss in the Car?
When your car is leaking fluid, you shouldn’t drive it. Instead, tow your vehicle to a garage or schedule car maintenance with a mobile mechanic to determine the cause of the leak.
That said, here’s how you can identify different fluid leaks:
- Engine oil: If you see brown or black fluid leaking from under the engine bay, that’s the motor oil.
- Radiator coolant: A puddle of green or red fluid under the car’s engine is usually the coolant. Remember that engine coolant is toxic to humans and animals, so handle it cautiously.
- Automatic transmission fluid: A reddish fluid leaking under the car’s center is mostly the transmission fluid and may smell similar to gasoline.
- Power steering system fluid: If a slick reddish fluid leaks from under the hood, it’s likely the power steering fluid.
- Brake fluid: A puddle of dark brown liquid near the wheels or the car’s center indicates a brake fluid leak.
- Windshield wiper fluid: This fluid has a water-like consistency and is often brightly colored. When your car’s wiper fluid leaks, the liquid pools in the front.
- AC refrigerant: If you spot a colorless liquid under the hood, inside the cabin, or underneath the car, it might be an AC refrigerant leak. It has a strong, musty odor.
- Differential fluid: An amber or dark brown thick fluid leaking from under the car may indicate a differential fluid leak.
- Transfer case fluid: A blue, brown, green, or yellow fluid leaking from the area near the transmission is the transfer case liquid.
Maintain Optimum Car Fluid Levels with AutoNation Mobile Service
These nine fluids are your vehicle’s lifeblood, and driving with low fluid levels can lead to expensive repairs. So, it’s best to get routine fluid checks to protect your car from severe damage.
Don’t feel like driving to a garage?
That’s okay! The technicians from AutoNation Mobile Service can inspect and refill car fluids right from your driveway.
We’re a mobile auto repair solution offering competitive upfront pricing and a 12-month | 12,000-mile warranty on all services.
Contact us to replace your car’s engine fluids or refill the coolant reservoir.