What Are the Most Important Car Fluids to Check?

Under every car’s hood, you’ll find a veritable nest of hoses and reservoirs filled with fluids, every one of them engineered to fulfill a specific role. And a part of being a responsible car owner is checking the fluid levels and replenishing them when necessary. 

Important Car Fluids to Check

Older cars need more frequent checks and maintenance because they tend to use more of these fluids and develop leaks with age. But their engine bays allow for easier identification of the various fluid reservoirs and easier access to measurement dipsticks. They’re also simpler to work on if you’re a do-it-yourself type.

Newer cars often have a plastic engine cover or shroud covering the mess of mechanicals. This makes the engine bay look neat and finished, and also makes it more challenging to identify and check various components. Apparently, automakers assume that a professional will service more complex modern vehicles at specific intervals outlined in the owner’s manual, or when a sophisticated self-diagnostic test warns you of a particular problem through an alert appearing on your smartphone.

In either case, opening your vehicle’s hood and acquainting yourself with the various fluid reservoirs can help you proactively keep your car in top shape. These are the primary fluids that a vehicle needs to run at peak performance.

Engine Oil

Inside of your engine, many moving parts create friction. Oil lubricates these components and reduces friction, making it the lifeblood of your engine. It is normal for a car to use a little oil, and for oil to get dirty. This is why you should check your oil regularly to make sure your engine has enough of it, and that it remains clean. 

You can check your engine’s oil using the dipstick. Park the car on a level surface, pull the dipstick out of the engine’s oil reservoir, wipe the dipstick clean, put the stick back into the reservoir, and pull it out again. You’ll find fresh oil at the bottom of the dipstick, along with markings that indicate whether the reservoir contains an adequate amount of it or not.

If the engine oil is low, unscrew the oil cap and add small amounts of the proper oil until the dipstick measurement shows enough in the reservoir. Also, the oil on the dipstick should be light brown with a fluid viscosity. If the oil is dark brown or even black, or doesn’t easily drip from the dipstick, you are well beyond the time to get an oil change.

Older vehicles require more frequent oil changes than newer vehicles. Oil change frequency also depends on how you drive the car. Be sure to consult your owner’s manual for the car manufacturer’s recommendations.

Engine Coolant

An internal combustion engine creates a series of explosions to make its power. As you can imagine, this process also creates plenty of heat, as does the friction of the engine’s moving parts. Coolant, or antifreeze, is what disperses this heat, making it the second lifeblood of your car’s engine.

Coolant flows through the engine, carrying the heat to the radiator. Fresh air flows into the radiator through the front grille, chilling the coolant before it makes another trip through the engine. It is vital to make sure nothing blocks your grille and other air intakes to maximize engine cooling.

Never check your coolant when the engine is hot, as this could result in injury. When the engine is cold, open the hood and inspect the coolant reservoir. This component is typically made of opaque plastic and has measurement indicators that tell you whether there is enough coolant or if you should add coolant.

Optimally, you’ll need to check your engine’s coolant every 50,000 miles. Also, the process and the type of coolant can vary by car, so be sure to check your owner’s manual to make sure you’re using the correct method and materials for your vehicle.

If the coolant gets low, the car might overheat, which will damage the engine. A temperature gauge or warning light on your dashboard will let you know if the engine is overheating. Pull over as soon as it is safe to do so and turn off the engine. As logic dictates, and to avoid injury, allow the engine to cool off before opening the coolant reservoir or the radiator.

Transmission Fluid

Similar to the engine, a car’s transmission has many moving parts that create friction. Transmission fluid lubricates these parts, reducing both friction and premature wear. A change in transmission shifting behavior merits a check of the transmission fluid. 

Older cars have a dipstick that allows you to check the fluid level and fluid quality using the same methodology for checking the oil. Newer cars require a mechanic to check the fluid level and quality, and some modern vehicles have completely sealed transmissions that never require a fluid check for the lifetime of the car.

Brake Fluid

Car braking systems use hydraulic pressure to apply the brakes. Brake fluid moves through chambers and hoses to translate the driver’s request for braking at the pedal into the application of the brakes at the vehicle’s wheels. But irregularities in the fluid, whether the system has a leak, water has seeped in, or air is stuck in the system, can negatively affect braking performance. 

Check your brake fluid if your brake pedal feels mushier than usual, or if you experience a decrease in stopping action. The fluid could be contaminated or at lower levels than required. Making sure your brake fluid is in top condition could be as important as the effectiveness of your brake pads and calipers. 

Power Steering Fluid

While many modern cars use electric steering systems, there are still plenty of vehicles on the road equipped with traditional power steering. To make it easier to turn the steering wheel, power steering uses a hydraulic system with power steering fluid. If your car’s power steering suddenly feels heavy and hard to turn, this may indicate low power steering fluid levels or a leak somewhere in the system. The condition merits a check of the power steering fluid reservoir before visiting a mechanic.

Windshield Washer Fluid

Most likely, the most common fluid you’ll check underneath your car’s hood is the windshield washer fluid. Depending on where you live and how much you drive, you’ll regularly consume this fluid as you clean your windshield of bugs, grit, and dirt. Running low on this fluid impacts your ability to drive but doesn’t harm the vehicle’s mechanical components. 

You’ll know when it’s time to add washer fluid. You’ll see a warning light on your dashboard, and the windshield washer jets will stop working. Experts recommend refilling the washer fluid reservoir with official washer fluid instead of water. Except in extreme temperatures, washer fluid doesn’t freeze. It’s also easy to find at just about any gas station or auto parts store. Adding more to your car is as easy as finding the proper reservoir, opening the cap, and filling it up.

While most modern vehicles require little in the way of problem diagnosis or action on the part of their owners when it comes to vehicle maintenance, it’s always helpful to understand what the most important car fluids are to check, and why. Proactively examining the various fluid levels in the reservoirs under your car’s hood can help to prevent expensive repair bills later, while offering added peace of mind while driving your car today.