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

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.

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.

Some fluids are topped up during your service. Ensuring your car is regularly serviced is key to making it run longer and shows it’s been well looked after to potential buyers. Take a look at our ‘ultimate car servicing guide’ for advice on how to ensure your car is serviced properly.

What are the 3 types of car engine oil?

The most common types of engine oil are 10W-30, 5W-30, and 0W-20.

  • 10W-30 is a conventional oil that is suitable for most cars. It is a good all-around choice that provides good protection for both hot and cold weather.
  • 5W-30 is a synthetic oil that is also suitable for most cars. It is thinner than 10W-30, which makes it a good choice for cars that operate in cold weather.
  • 0W-20 is a synthetic oil that is designed for cars that require the thinnest oil possible. It is not recommended for cars that operate in hot weather, as it may not provide enough protection.
  • 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.

    Checking your oil

    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 brown colour or appears to contain any thick deposits, this could mean it’s contaminated by water or other substances and you should get your engine checked immediately.   

    When the oil light on your dashboard comes on while you are driving, it might mean your vehicle has low oil pressure. This drop in oil pressure could be a sign of a few things: you are low on oil, your oil is dirty, or you have an oil leak. Whatever the possible reasons it’s essential that you have the vehicle checked by a professional as soon as possible. Don’t continue to drive the vehicle in this state as it could invalidate your warranty and ultimately lead to the engine seizing.

    While the image that represents the oil warning light will differ from car to car (it’s worth checking your car manual to confirm what the oil light looks like), it will typically feature on the dashboard and will resemble an old-fashioned oil can. In some vehicles, there may even be the word ‘OIL’ under or next to the light.


    Over half the energy produced by your car is converted into heat. Engine coolant (Anti Freeze) 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! 

    What are the main different types of engine coolant?

    All coolants contain a mix of water, antifreeze agents (such as ethylene glycol or propylene glycol) and corrosion inhibitors, of which there are several types:

    • Inorganic Additive Technology (IAT) – Conventional low-silicate coolants used by traditional and classic vehicle iron and steel engines .
    • Organic Acid Technology (OAT) – OAT coolant works better with modern (post 2000) aluminium engines
    • Nitrated Organic Acid Technology (NOAT) – suitable for heavy-duty and diesel engine applications.
    • Hybrid Organic Acid Technology (HOAT) – suitable all types of cars

    If you are unsure what engine coolant your vehicle needs consult your car owner manual or contact your local garage to make sure. Always take the suggestion of the car manufacturer or an experienced technician before choosing a coolant.

    Engine Oil in your Coolant

    If you find engine oil in your car coolant reservoir, there are a range of potential reasons, including damaged cylinder head gaskets, damaged cylinder heads the presence of too much water in the engine, or even excessive overheating. Always consult with your mechanic or local garage if you discover oil in your coolant. 

    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.  

    Power Steering Fluid

    Power steering fluid is the fluid used in the power steering system to create a hydraulic link between the steering wheel and the front wheels, making it easier to turn.

    If you notice your vehicle is becoming difficult to steer it’s important to check that the fluid level isn’t low or empty. 

    What types of Power Steering Fluids are there?

    There are three types of power steering fluids that are used in most modern cars;

    • Automatic transmission fluid (ATF). The same fluid used for automatic transmissions can be used in some power steering systems.
    • Synthetic power steering fluid. Most newer vehicles use synthetic fluid that is created in a lab. These varieties are usually engineered for specific types of cars or steering systems.
    • Non-synthetic, mineral power steering fluid. Mineral hydraulic fluid may be used in some instances that accept ATF.

    Please refer to your owner’s manual to learn which type of power steering fluid to use in your car. Choosing an incompatible fluid can permanently damage the power steering system. Be sure to select a replacement steering fluid appropriate for your vehicle.

    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. 

    What are the types of brake fluid?

    There are four main types of brake fluid;

    • DOT 3 – suitable for most driving conditions and also older vehicles without ABS systems
    • DOT 4 – suitable for high-performance vehicles and vehicles with ABS systems.
    • DOT 5 – not for regular everyday use. It is designed specifically for race cars and other performance-based vehicles. 
    • DOT 5.1 – can be used in both on-road and off-road motorcycles, as well as passenger cars and commercial vehicles.

    It’s very important that you use the correct brake fluid in your vehicle. Please refer to your car owner’s manual to learn which type of brake fluid to use in your car. If you are still unsure contact your main dealer.

    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. 

    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. 

    What are the three types of transmission fluid?

    In general, there are three main types of transmission fluids: automatic transmission fluid and manual transmission fluid.

    • Manual transmission fluid – generally used in older vehicles and vehicles with manual (standard) transmissions
    • Automatic transmission fluid (ATF) – made for vehicles that use automatic transmissions but can be used in vehicles with manual transmissions as well
    • Continuously variable transmission fluid (CVT) – a high performance, fully synthetic transmission fluid designed to work in a wide range of continuously variable transmission (CVT) equipped passenger vehicles.

    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!

    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 manufacturer’s 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.  

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