6 Essential Fluids That Keep Your Car Healthy and How to Maintain Them

Did you know that your car uses 6 essential fluids in order to keep it running efficiently?

  • Engine oil
  • Coolant
  • Power steering fluid
  • Brake fluid
  • Transmission fluid
  • Windscreen washer fluid

Cars need regular maintenance and it's the fluids that often need the most attention. They play a huge role in keeping your vehicle running as smoothly as possible and that's why it's important to change them regularly and dispose of the old fluids correctly, otherwise they could cause harm to the environment.

refilling engine oil

Engine Oil

Oil is your cars most important fluid; it reduces friction inside the engine and ensures everything stays running efficiently. It also protects the moving parts of your engine from getting damaged by heat and its cleaning properties can help to reduce dirt from clogging up the engine openings.

How to check your oil:

Before checking your vehicles engine oil, it's important to check the owner's manual and make sure you have the correct type of oil for your car.

Firstly, make sure you're parked on a level surface and that your engine has been off for a while so it's not hot - a cool engine gives the oil enough time to settle at the bottom of the sump, giving you a more accurate reading.

Most cars will have a dipstick to give you a reading of the oil in the engine. It’s important to remove the dipstick first and wipe off any oil with a cloth. Then put the dipstick back in and when you remove it again, you’ll be able to see your oil level based on the maximum and minimum indicators. If your oil is below minimum, this could indicate that your engine is leaking, and you’ll need to add more oil immediately. However, you’ll need to be very careful not to overfill the oil as this could damage the engine.  

Remember, don’t just check the quantity of the oil, you should also check the quality! If the oil has changed from its normal amber colour to a milky colour or appears to contain any thick deposits, this could mean it’s contaminated and you should replace it.   


Over half the energy produced by your car is converted into heat. Engine coolant helps to prevent your engine from overheating by absorbing that heat and expelling it through the exhaust. Without coolant, your engine would reach temperatures beyond its tolerance levels.  

It’s not just heat that engine coolant protects against either; it also helps protect your car in the winter months as it’s resistant to freezing. Win-win! 

How to check your coolant:

Like checking your oil, it’s important to make sure your engine isn’t hot when checking your coolant levels. If your engine is running or hot, do NOT attempt to open the radiator cap – the system is highly pressurised and the fluid inside is extremely hot which could cause severe burns.

Once it’s safe to do so, you can observe the level of fluid using the minimum and maximum markers on the coolant tank. If the fluid lies below the minimum mark, carefully remove the radiator cap using a cloth and check if the coolant is visible. If the fluid level isn’t near the top, you will need to re-fill the tank until you can see the level is back between the minimum and maximum markers. Again, it’s important to ensure you’re using the correct coolant grade for your vehicle when refilling.  

removing coolant cap

Power Steering Fluid

Another important fluid that helps keep your car healthy is the power steering fluid. This transmits power to the steering system and allows your vehicle to steer effortlessly. If you notice your vehicle is becoming difficult to steer it’s important to check that the fluid level isn’t low or empty. 

How to check your power steering fluid:

First, you should check your owner’s manual – this will tell you where the reservoir is located and which type of fluid you’ll need.  

To check the fluid level, you’ll need to locate the power steering reservoir. Most reservoirs have level markings on the side and some have both ‘hot’ and ‘cold’ level markings. Tip – if the vehicle has not been driven for at least 8 hours, use the cold reading, otherwise, use the hot level reading.  

To refill the fluid, use a funnel and slowly pour it into the reservoir and make sure to keep checking the level to prevent it from overfilling.  

Brake Fluid

Brake fluid is one of the most essential fluids your car needs. Without brake fluid, your vehicle would not be able to stop when you push the brake pedal. Braking is supposed to happen instantly. So, if you find that there’s any delay or abnormal feeling in your brakes – this fluid is the first thing you should check. 

How to check your brake fluid:

Brake fluid requires regular changes as recommended by your repairer – normally every 2 years maximum – as it can become contaminated with water over time due to it being hygroscopic (absorbing moisture from the air). This excess moisture can cause brake lines to rust, ultimately affecting the performance of your brakes.  

Most cars have a brake fluid reservoir in the engine bay; to check this you just need to look at the colour and level of fluid. Brake fluid should be transparent, not cloudy or dark. Similar to the other fluids, you need to make sure the level falls between the minimum and maximum indicators. If the fluid is below minimum, add more but first ensure it’s the right type for your car.  

Tip – if the brake fluid has dropped, this could be an indication that your brake pads might need replacing. 

checking brake fluid

Transmission Fluid

The transmission fluid serves a similar purpose to the engine oil; it protects and cools the components inside your transmission. There are several different types of transmission fluid, which is why it’s important to use the fluid recommended in the owner’s manual of your vehicle to achieve the best performance. 

How to check your transmission fluid:

Most manual transmission cars don’t have a dipstick for transmission fluid, unlike automatic transmission cars. The majority of manual vehicles will require a professional mechanic to change this fluid and this may only be necessary in the event of a repair or service as they are generally factory-filled with no top-up required.  

We would not recommend changing your own transmission fluid unless you are a qualified mechanic as this can be very dangerous. 

Windscreen Washer Fluid

Windscreen washer fluid doesn’t have any effect on your vehicle’s performance, it’s simply used in cleaning the windscreen while the vehicle is being driven and therefore, is crucial for safe driving. Did you know, it’s illegal to drive your car without windscreen fluid in?!

How to check your windscreen washer fluid:

This is the easiest fluid to change - you simply open the car bonnet and look for the washer fluid reservoir, it’s usually located towards the back of the engine bay. Simply pour the fluid into the reservoir until it’s full and close the cap. Job done!

adding screen wash

All the fluids in your vehicle should be checked at least at every oil change interval and some more often, as and when required. These fluids are vital in keeping your car in great working order. 

If your car is over 3 years old, the chances are your manufacturers warranty will have expired, leaving you open to unexpected breakdowns and garage repair bills. Protect your vehicle with the UK’s best used car warranty from Warrantywise for complete peace of mind and worry-free motoring. 

For a quick quote or more information, visit our Car Warranty page.