Everything You Need To Know About Car Fluids

When you own a car, it’s important to remember that it doesn’t just run on fuel. In fact, for a car to remain healthy and even operational, it needs many other substances, collectively known as car fluids. 

Depending on your car, it could use up to 5 essential fluids to keep it running well. If you neglect and fail to maintain even one of these fluids, your car’s performance and safety could suffer. 

To ensure that your vehicle is well looked after, here’s everything you need to know about car fluids and what you need to do to maintain them properly. If you need other maintenance tips, you can find more here on Car Adviser.

In this guide

What are the different types of car fluids?

There are multiple types of car fluids that you’ll need to keep topped up and be aware of. Here are the main five that your car will likely have, as well as information about how to check them and what to look out for. 

Engine oil 

Your engine doesn’t just need fuel to power your car. It also requires oil. When your engine is running, there are a lot of moving parts that are rubbing against each other. These parts need to be well lubricated to avoid friction, which can cause an excess amount of heat within your engine system. Oil is slippery and is thus used to keep the engine well-lubricated so that everything runs smoothly within it. 

Not only does engine oil stop your engine from overheating, but it also protects the parts within it from damage and wear caused by excessive contact. Engine oil also has a cleaning property, as it can help stop dirt and carbon from clogging up the engine system, helping to ensure that your car performs well. 

With enough oil, your engine could get dry, causing issues and potential damage that can be costly to fix; that’s why you need to keep this car fluid topped up. That said, it’s also vital that you use the right oil for your vehicle, so make sure to check your car’s handbook before filling it with oil. 

How to check engine oil

To check your engine oil, you first want to ensure that your car is off, parked on a level surface and that the engine is cold. This is because a cold engine gives the oil enough time to settle in a sump. 

When checking your engine oil, the main thing you’re looking for is to see if you have enough in your car. To do this, you’ll measure the amount of oil you have with a dipstick. Your dipstick will be located under your bonnet, and this device will have two marks that indicate the oil’s minimum and maximum depth. 

To measure your oil level, you need to dip the dipstick into the engine oil sump. Once you remove the stick, oil residue should be left on it. Your oil level is fine if the residue is found between the maximum and minimum indicators. If it’s under the minimum indicator, it may suggest that your engine has a leak and that it needs to be replaced immediately. 

You should also check to see if the oil on your dipstick is an amber colour. If it’s white and milky, it could be contaminated and needs to be replaced. 


Combustion is required for your engine to work and power the car. This creates a lot of heat, and if not managed, it can cause serious damage to the car. To stop your engine from overheating, a coolant fluid is used that absorbs the heat and expells it through your car’s exhaust. Without coolant, the components within your vehicle could reach huge temperatures, which may cause melting and defections. 

Coolant also has another purpose: it stops the car from getting too cold in the winter. Many coolants contain anti-freeze, which helps to protect your car’s parts from seizing up in the winter months. This means that coolant is basically a temperature regulator, keeping your car in just the right thermal condition. 

How to check coolant

Checking your coolant is very similar to checking the engine oil. You first need to ensure that your engine isn’t on and that it’s nice and cool. This is because a warm engine can cause pressure that, when released when opening the radiator cap, can cause hot fluid to shoot out, potentially causing burns.

To check, you simply need to locate your coolant tank – which is again under the bonnet – and see if the fluid rests between the minimum and maximum markers on the cap. If the fluid reservoir is under the minimum, you’ll have to refill it. Make sure to remove the radiator cap with a cloth, as the fluid can irritate your skin. Also, when refilling, make sure to use the proper coolant grade for your car, which you can find in your handbook. 

Power steering fluid 

Modern cars, especially those that are powerful and heavy, will come with power steering. This uses a hydraulic system that helps assist drivers in steering and controlling these vehicles easily. A hydraulic system requires fluid within it for it to work, which is why you must maintain the fluid level in your power steering. A lack of fluid can make your car much harder to steer, which could be a massive safety concern.

How to check power steering fluid

To check your power steering, you need to figure out where the fluid reservoir is located in your vehicle. You can use your manufacturer handbook for this or guides online. You’ll also need to know what type of fluid you will need, as using the wrong one can damage the whole system. 

Once you’ve located the steering reservoir, you’ll need to check the fluid inside it against various markings. Unlike oil and coolant, there are actually two different sets of markings: a pair for when the car and fluid are hot and another for when the car is cold. To get an accurate reading of your power steering level, always use the cold reading markers if your vehicle hasn’t been driven for at least 8 hours. If you’ve used it before that time, measure it against the hot markers. 

There are two sets of measurements because the fluid can expend under different thermal settings. If you need to refill the fluid, use a funnel and slowly pour some in. Make sure not to overfill it.

Brake fluid

Brake fluid is an essential part of your car, as, without it, your entire brake system will be useless and won’t be able to stop your car effectively. Making sure that your brake fluid is at the right level consistently is an essential maintenance task, as it ensures that your vehicle is safe to drive. 

If there’s a delay or an abnormal feeling when you push your brake pad, then one of the first things you should check is your brake fluid. Even if there is no obvious issue, it’s recommended that your brake fluid is replaced every two years at least.

This is because the fluid can easily be contaminated by water that’s absorbed by air moisture, which can lead to rust within your brake system. Typically, your car will have its brake fluid replaced in a car service or MOT, which you can learn more about here on Car Adviser.

How to check the brake fluid 

The brake fluid reservoir is usually found in your car’s engine bay. To check it, you first need to see if it’s the right colour. Brake fluid should be clear, so if yours is cloudy or dark, that’s a sign of a problem. 

Like all other types of fluid in a car, you must check that you have the right amount. Look to see if the fluid level sits between the minimum and maximum indicators in the reservoir.

If it’s below the minimum marker, add more, but ensure you’re using the right brake fluid for your car before you do this. If there’s been a significant drop in fluid level, it may indicate that your brake pads need replacing. 

Windscreen washer

Although it doesn’t help your car function or drive, the windscreen washer fluid in your car is potentially one of the most important in terms of safety. This is because this fluid helps to keep your windscreen free from debris and dirt. If you haven’t got enough screenwash, you may be unable to clear off any grim on your windscreen, which can affect your visibility and make your drive a bit more dangerous. 

It’s important to take your windscreen washer fluid seriously, as driving without any in your car is actually illegal and can result in a fine and points off your license. 

How to check the windscreen washer fluid

Screenwash for your car is perhaps the easiest fluid to check. You first need to find your washer fluid reservoir, which is commonly at the back of your engine bay, and then check to see if it’s between the minimum and maximum markers. If you need more, you can simply pour it into this reservoir until you have enough and then close the lid. 

Be aware that you may have to dilute screenwash in water before using it. Check the instructions on the screenwash you have to see how much water you need to add to make sure that it’s not too strong and not too weak. 

Car Fluids FAQs

All of the fluids of a car are important, as, without even one of them, the performance and safety of your car will suffer. However, most people in the auto industry consider engine oil to be the most important fluid. This is because, without it, your engine could start to break down and get damaged, making your vehicle inoperable. 

Coolant comes in a close second in terms of importance because that stops the car from overheating. Without enough coolant, your engine could reach massive temperatures that can also damage the engine system, causing the entire car to break down. 

With that said, there's no fluid that you should prioritise over the other. All of them should be over their minimum level at all times, and you should also check to make sure they've not become defective or compromised.

When your fluids are low, it's best to change them and refill them. However, it can be hard to know when it is best to check them, as your fluids can all drain at different rates. 

It's said that it's best to check on your fluids every 30,000 miles to see if they're still in good condition and if you have enough. However, certain fluids have different timespans. 

For example, it's said that you should change your brake fluid every two years because it can easily get contaminated with water. Thankfully, if you have a modern car, you'll likely get alerted when you need to change and refill a certain fluid, as you'll have a warning light appear on your dashboard.

When refilling any type of car fluid, it's essential to use the correct one for your specific car. This is because using the wrong one could cause issues and mean that your car doesn't perform properly.

Using the type of fluid that isn't right for your car can result in poor lubrication, overheating, and even transmission failure. Furthermore, a mechanic might not be able to fix the damages caused by this, so it's definitely something you need to avoid. 

However, what's even worse is putting the wrong fluid into the wrong reservoir, such as putting brake fluid where your oil is meant to go. This can cause serious issues if not spotted and repaired quick enough, resulting in a substantial mechanical bill that your insurance or warranty isn't likely to cover due to it being considered accidental damage.

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