The Ultimate Guide To Car Fluids

The Ultimate Guide To Car FluidsLike us, cars need to stay hydrated, however it isn’t just water that they need. Cars have been getting more efficient and reliable, but they still need some maintenance. Fluids play a massive role in keeping your car running smoothly, from the brakes to the engine. Make sure top them up to keep your vehicle in top shape. There is a number of fluids to check, for example:

  • Coolant
  • Engine oil
  • Power steering fluid
  • Brake fluid
  • Transmission fluid
  • Washer fluid

Popping the bonnet and checking the fluids can help to keep your vehicle running well and at a lower risk of breaking down.

Let’s go through the fluids, how to check them, and how to top them up:

Engine Coolant


Coolant keeps your engine cool, which is important for efficiency, emissions, and most importantly to reduce wear and tear within your engine. Protecting the engine from overheating means you won’t be stuck with a nasty repair bill.

You should only have to check this fluid regularly, preferably every month, although this can be sooner because of a leak. You may also want to check the coolant during the summer, where leaks can be exacerbated by the overworked cooling system.

Warning: Never check your coolant while the engine is hot. You risk personal injury.

Under the bonnet, you should see a clear, or opaque container. It should have a min and max reading on the side, with the level of the liquid visible. If below the min line you will need to fill it to the max line, with a mix of water and coolant. If there is no container then you need to open the radiator cap to see if the coolant reaches the top.

Make sure any coolant you use is approved for your vehicle, and when opening the radiator, leave for a minute to release any trapped air bubbles.

To fill up on coolant, you have to unscrew the reservoir, and for most cars pour in a 50:50 mixture of water and coolant. The mixture does differ across car models so make sure to always check your car’s service manual. If you only have water to hand then this will work for a few miles but you should urgently seek out a nearby garage who will top you up with coolant.

Low levels of coolant may mean there is a leak in the system, which you can find by checking around a cool engine to find wet patches.

Engine oil


The parts in your car’s engine rotate and move up and down several times a second. This requires a lot of pumps, cylinders and other moving parts. All these moving parts rub together. Oil helps protect the system from wear and tear, while also making the parts work better, by lubricating joints and friction points.

You should be checking the system once every month or so, since the check is relatively quick. This helps avoid any issues with leaking oil or dirty oil.

Advisory: Run the car for 5 minutes or around the block so oil flows through the system first.
Check your owner’s manual to find the dipstick. Pull the dipstick out and wipe it down with a towel or rag. Reinsert it, then pull it out to check the level of oil in the tank. The dipstick should display a normal range of oil.

If the oil is below the range, then fill the oil tank with oil designed to work with your vehicle. Make sure not to overfill the system as this will mean more leaks.

Low levels of oil could indicate a leak in the system, but dirty oil may mean components are starting to wear down. The oil should be yellow, or amber. Brown or dark oil may mean you need an oil filter replacement.

Power steering fluid


Turning an older car was a very heavy and exhausting task, as your arm muscles were responsible for a large part of turning the wheels on the ground. Modern cars have power assisted steering, to make the steering of the car much easier by making it lighter. Power steering makes turning easy at any speed, using hydraulic fluids to make the wheels turn.

Usually the power steering fluid doesn’t need to be replaced often, but spotting early signs of a leak could save your life. Since the fluid is crucial to the maneuverability of your car, you may slowly notice that turning becomes more difficult at low speeds, and a 3 point turn is more like a workout.

Just at the base of the windscreen, there is a small tank. If you can’t find it or are unsure about what it looks like then consult your owner’s manual. There should be an indicator on the tank, where you can see the minimum and maximum level of fluid. If this isn’t the case, then you will need to open the cap.

Warning: Before you add the new fluid, clean the area around the opening to avoid contaminating the fluid.
Use the power steering dipstick to check the level of power steering fluid in the tank. Simply, remove the dipstick, wipe it down, reinsert it and then check the level.

Low fluid levels will need to be topped up, but it is essential that you use hydraulic power steering fluid that is specifically suited to your vehicle.

Having only a little power steering fluid left will have a noticeable impact on how easily your car steers. The low levels may indicate a leak somewhere in the system.
Brake fluid
Brake fluid acts as a pressurised step between your foot on the pedal and the brake rotors. This helps you brake more instantly and with less effort.

You shouldn’t have to check the brake fluid at all, but spotting a leak may just save your life from faulty brakes. Over time, brake fluid can become contaminated. Water, for example will cause the brake lines to rust resulting in the fluid becoming contaminated. Dark fluid is a serious sign that the system needs a mechanic.

You can find the brake fluid reservoir near the back of the engine compartment. In most cars the container will be opaque, with a clear max-min lines.

Warning: Before you add the new fluid, clean the area around the opening to avoid contaminating the fluid.

Open the reservoir, and check that the fluid almost fills the tank. Top it up with the right fluid, consult your owner’s manual if you need some guidance.

Transmission Fluid


Similar to engine oil and power steering fluid, the transmission fluid lubricates and cools components in your car. The transmission system contains gears, clutches and valves which must move seamlessly while driving.

Transmission fluid should last the lifetime of the car, but may begin to leak due to a knock or crack.

Your vehicle should have another dipstick to check the transmission fluid level. You should remove it from the system, wipe it down, reinsert it then check the level of fluid. Additional checks should be done on the colour, dark, cloudy or gritty fluid requires a mechanical diagnosis by a mechanic.

Top up the transmission fluid by pouring your vehicle specific transmission fluid into the fill tube. Run through the gears to let the new transmission fluid flow through the system. This can be a tricky job, if it not carried out correctly it can damage your transmission, leading to extra repair costs. It is advisable to get help from a professional mechanic to carry out the work if you’re not sure how to do it.

Low transmission fluid can cause rough shifting, odd noises when switching gears, and uncontrolled surges (in case of an automatic transmission).

Windscreen washer fluid


Windscreen wiper fluid might not be vital but it is important to your windscreen. Dirt builds up, and a little British rain doesn’t quite keep the glass clear. Windscreen washer fluid polishes your window to ensure there is greater clarity to your vision.
You may have to check on the amount of this every few months, and even more in the summer.

Luckily, it’s the easiest to top up since the washer tank bottle is easy to find and normally doesn’t require a specific type of fluid.
Under the bonnet, there will be an opaque tank, usually labelled “washer” or “windscreen”. Pop the lid open and check the amount of fluid. If you are low simply pour more washer fluid in. You can use soapy water, but this will slightly damage the system, so only use it in emergencies.

Going without washer fluid will mean your windscreen slowly piles on layers of dirt. Windscreen wipers only cover a certain amount of the glass, so eventually you build up “dirt goggles”

Fuel is the most important fluid in cars at the moment although, your other fluids are also vital to your car running well. Make a schedule to check the different fluids around your vehicles, and make sure to stick to any recommended service schedule. If you suspect there is an issue with a system, then get a Clickmechanic diagnostic inspection.