Regularly checking your car fluids is one of the most important maintenance tasks you can perform to keep your vehicle running smoothly and safely. Whether you’re a new driver or an experienced motorist, understanding what fluids a car needs and how to monitor fluid levels in car systems can save you from costly repairs and potentially dangerous breakdowns.
What are the key car fluids?
Modern vehicles rely on several essential fluids to operate safely and efficiently. Each fluid serves a specific purpose: lubricating moving parts, cooling the engine, and enabling you to stop safely. Understanding what fluids a car needs is the first step toward proper vehicle maintenance.
The five most critical fluids you should regularly monitor include:
Engine oil - Lubricates the engine’s moving parts and prevents overheating.
Windscreen wash - Keeps your windscreen clean for optimal visibility.
Coolant - Regulates engine temperature and prevents overheating.
Power steering fluid - Enables smooth, easy steering.
Brake fluid - Transfers force from the brake pedal to the braking system.
Each of these fluids has specific checking procedures and replacement intervals. Neglecting any of them can lead to reduced performance, component damage, or even complete system failure. The good news is that checking most car fluids is straightforward and requires minimal tools or mechanical knowledge.
1. Engine oil
Engine oil is arguably the most critical fluid in your vehicle. It lubricates the engine’s moving parts, reduces friction, helps dissipate heat, and prevents the buildup of harmful deposits. Checking your engine oil regularly is essential for maintaining engine health and avoiding catastrophic failure.
How to check engine oil
To properly check your engine oil level, follow these steps:
Step 1: Park on level ground – Ensure your car is parked on a flat surface to get an accurate reading. An uneven surface will give you a false reading of the fluid level in car measurements.
Step 2: Turn off the engine and wait – After driving, allow the engine to cool for at least five to ten minutes. This gives the oil time to settle back into the oil pan, providing a more accurate reading.
Step 3: Locate the dipstick – Open your bonnet and find the engine oil dipstick, usually marked with a brightly coloured handle (often yellow or orange) and labelled “ENGINE OIL.”
Step 4: Remove and wipe the dipstick – Pull the dipstick out completely and wipe it clean with a lint-free cloth or paper towel.
Step 5: Reinsert and check – Push the dipstick all the way back in, wait a moment, then remove it again. Check where the oil level sits between the minimum and maximum markers.
Step 6: Assess the oil condition – While checking the level, also examine the oil’s colour and consistency. Fresh oil is amber-coloured and relatively clear. Dark, dirty oil or oil with a milky appearance may indicate problems.
What to look for
The oil level should sit between the minimum and maximum marks on the dipstick. If it’s below the minimum mark, you need to add oil immediately. If it’s above the maximum, you may have overfilled the engine, which can also cause problems.
The oil’s appearance reveals its condition. If the oil is very dark or gritty, it’s time for an oil change. If you notice a milky or frothy appearance, it could indicate coolant contamination and require immediate professional attention.
How often to check
Most manufacturers recommend checking your engine oil at least once a month and before any long journeys. However, older vehicles or those with known oil consumption issues may need more frequent checks. Making this part of your regular vehicle maintenance routine will help you catch problems early.
2. Windscreen wash
While windscreen wash might seem less critical than other fluids, it plays a vital role in road safety. Clear visibility is essential for safe driving, and windscreen wash helps remove dirt, insects, and road grime that can obscure your view.
How to check the windscreen wash
Checking your windscreen wash fluid is one of the simplest maintenance tasks:
Step 1: Locate the reservoir – Open your bonnet and find the windscreen wash reservoir. It’s usually a translucent plastic container marked with a windscreen symbol. The cap is often blue or has a windscreen wiper icon.
Step 2: Check the level – Most reservoirs are translucent, allowing you to see the fluid level without opening them. Look for minimum and maximum markers on the side of the container.
Step 3: Top up if needed – If the level is low, simply pour windscreen wash fluid into the reservoir until it reaches the maximum line. You can use pre-mixed windscreen wash or dilute concentrated wash according to the manufacturer’s instructions.
Choosing the right windscreen wash
Different windscreen wash products are available for various conditions:
Summer wash – Effectively removes insects and road film.
Winter wash – Contains antifreeze to prevent freezing in cold weather.
All-season wash – Provides year-round protection and cleaning.
Never use plain water alone, as it doesn’t clean effectively and can freeze in winter, potentially damaging your washer system. Also, avoid using washing-up liquid, as it can damage rubber seals and leave residue on your windscreen.
How often to check
Check your windscreen wash level weekly, especially during winter months when you’ll use it more frequently. Keeping this reservoir topped up is a simple way to ensure you maintain clear visibility in all driving conditions.
3. Coolant
Coolant, also known as antifreeze, is essential for regulating your engine’s temperature. It prevents overheating in summer and freezing in winter, while also protecting the cooling system from corrosion. Maintaining the correct coolant level is crucial for preventing engine damage.
How to check the coolant
Warning: Never check coolant when the engine is hot, as the system is pressurised and opening the cap can cause serious burns.
Step 1: Locate the coolant reservoir – Find the coolant expansion tank, usually a translucent plastic container near the radiator. It typically has minimum and maximum level markers.
Step 2: Check the level – With the engine cold, look at the reservoir's side to see where the coolant level sits. It should be between the minimum and maximum marks.
Step 3: Check the colour – Coolant comes in various colours (pink, red, orange, green, or blue). It should appear bright and clear. Rusty or murky coolant indicates contamination or degradation.
When to top up
If the coolant level is below the minimum mark, you’ll need to top it up. Use the correct type of coolant for your vehicle (check your owner’s manual) and ensure it’s properly diluted if required. Some coolants come pre-mixed, while others need mixing with distilled water.
For a more detailed guide on coolant maintenance, including how to flush your cooling system and identify coolant-related problems, see our comprehensive car coolant guide.
How often to check
Check your coolant level monthly and before long journeys. If you find yourself frequently topping up coolant, this indicates a leak that requires professional attention.
4. Power steering fluid
Power steering fluid enables the hydraulic system that makes steering your vehicle effortless. Without adequate fluid, steering becomes heavy and difficult, potentially creating dangerous situations, especially at low speeds or when parking.
How to check power steering fluid
Step 1: Locate the reservoir – Find the power steering fluid reservoir under the bonnet. It’s usually a small plastic container with a cap marked “POWER STEERING” or with a steering wheel symbol.
Step 2: Check when cold – For the most accurate reading, check the power steering fluid when the engine is cold. Some reservoirs have separate markings for hot and cold readings.
Step 3: Examine the level – Most power steering reservoirs are translucent with minimum and maximum markers. The fluid level should sit between these marks.
Step 4: Assess the colour – Power steering fluid is typically red, pink, or amber when new. Dark or dirty fluid may need to be changed, while a milky appearance could indicate moisture contamination.
Important considerations
Some modern vehicles use electric power steering systems that don’t require fluid. Check your owner’s manual to determine what type of system your vehicle has.
If you notice the power steering fluid level dropping regularly, you likely have a leak in the system. Common leak points include hoses, connections, and the power steering pump itself. These issues require professional diagnosis and repair.
How often to check
Check your power steering fluid every three months or according to your vehicle manufacturer’s recommendations. If you notice any changes in steering feel, such as increased effort, noise, or vibration, check the fluid level immediately.
5. Brake fluid
Brake fluid is perhaps the most safety-critical fluid in your vehicle. It transfers the force from your brake pedal to the brake callipers or drums, enabling you to stop safely. Maintaining proper brake fluid levels and quality is essential for your safety and that of other road users.
How to check brake fluid
Step 1: Locate the brake fluid reservoir – typically mounted on or near the brake master cylinder at the back of the engine bay. It’s usually a small translucent plastic container with a cap marked “BRAKE FLUID” or with a brake symbol.
Step 2: Check the level – Look at the side of the reservoir to see the fluid level. It should sit between the minimum and maximum markers. You shouldn’t need to remove the cap to check the level.
Step 3: Examine the colour – Fresh brake fluid is clear or slightly amber. If it appears dark brown or black, it’s contaminated and needs to be changed. Brake fluid naturally absorbs moisture over time, reducing its effectiveness and potentially causing corrosion in the braking system.
When to take action
If your brake fluid level is significantly low, this could indicate worn brake pads (which is normal as the fluid fills the space created by pad wear) or a leak in the system. Either way, you should have your brakes inspected professionally.
Never top up brake fluid without understanding why it’s low. If you’ve recently had brake work done, topping up might be appropriate. However, if the level has dropped without explanation, there may be a leak or your brake pads may need replacing.
For more information on maintaining your braking system, read our guide on how to check brakes on your car.
Important safety notes
Only use the brake fluid type specified in your owner’s manual (usually DOT 3, DOT 4, or DOT 5.1)
Never mix different types of brake fluid.
Brake fluid is highly corrosive. Avoid contact with paintwork and wash off any spills immediately.
If you’re unsure about brake fluid levels or condition, seek professional advice immediately.
How often to check
Check your brake fluid level monthly and have the fluid completely replaced according to your manufacturer’s schedule (typically every two years). Regular checks help ensure your braking system functions properly when you need it most.
Car fluid check summary table
Here’s a quick reference guide to help you remember the key information about checking your car fluids:
Fluid | Location | Check frequency | What to look for | Typical colour |
|---|---|---|---|---|
Engine oil | Dipstick in the engine bay | Monthly | Level between min/max marks; clean, amber colour | Amber (new) to dark brown (used) |
Windscreen wash | Translucent reservoir with windscreen symbol | Weekly | Adequate level for visibility needs | Blue, pink, or green (varies by product) |
Coolant | Expansion tank near the radiator | Monthly | Level between min/max; bright, clear appearance | Pink, red, orange, green, or blue |
Power steering fluid | Small reservoir with steering symbol | Every 3 months | Level between min/max; clean fluid | Red, pink, or amber |
Brake fluid | Reservoir on the brake master cylinder | Monthly | Level between min/max; clear or light amber | Clear to light amber (new) |
General tips for all fluid checks:
Always check fluids with the vehicle on level ground.
Check most fluids when the engine is cold (except where noted).
Never remove radiator or coolant caps when the engine is hot.
Keep fluids away from your eyes and skin.
Dispose of old fluids responsibly at designated recycling centres.
Use only the fluid types specified in your owner’s manual.
If you’re topping up fluids frequently, investigate for leaks.
When to see a mechanic about car fluids
While checking car fluids is something most drivers can do themselves, certain situations require professional attention. Knowing when to seek expert help can prevent minor issues from becoming major problems.
Signs you need professional help
Rapidly dropping fluid levels – If you find yourself frequently topping up any fluid, this indicates a leak that needs professional diagnosis and repair. Small leaks can quickly become major problems, potentially leaving you stranded or causing expensive damage.
Contaminated fluids – Milky engine oil, rusty coolant, or very dark brake fluid suggest contamination or degradation that requires professional attention. These conditions can indicate serious problems, such as head gasket failure, cooling system corrosion, or brake system issues.
Unusual colours or smells – If any fluid appears an unusual colour or has a burnt smell, have it checked by a mechanic. For example, burnt-smelling engine oil might indicate overheating, while sweet-smelling coolant leaks can be toxic and require immediate attention.
Warning lights – If dashboard warning lights illuminate for oil pressure, engine temperature, or brake system issues, stop driving and seek professional help immediately. These warnings indicate potentially serious problems that could cause damage or compromise safety. Our guide on warning signs your vehicle needs attention provides more information on dashboard alerts.
Difficulty steering or braking – Heavy steering or a spongy brake pedal, even with adequate fluid levels, indicates problems within these critical safety systems that require immediate professional inspection.
Leaks under your vehicle – Puddles or stains under your parked car indicate fluid leaks. Different colours help identify the source: red or pink suggests transmission or power steering fluid, green or orange indicates coolant, and dark brown or black could be engine oil. All leaks should be investigated professionally.
Regular professional servicing
Even if you diligently check your car fluids yourself, professional servicing remains essential. Mechanics can:
Perform complete fluid changes at appropriate intervals.
Check fluid quality using specialised equipment.
Inspect for leaks and wear in fluid systems.
Test brake fluid moisture content.
Assess overall vehicle health beyond fluid levels.
Most manufacturers recommend professional servicing annually or at specific mileage intervals. Following these schedules, combined with your regular fluid checks, provides comprehensive vehicle maintenance.
Building a maintenance routine
Incorporating fluid checks into your regular routine doesn’t take long but provides significant benefits. Consider checking fluids:
On the first day of each month (easy to remember).
Before long journeys or holidays.
When filling up with fuel (especially windscreen wash).
After any warning lights appear.
Following any unusual vehicle behaviour.
You might also want to check other important aspects of vehicle maintenance, such as car battery health and tyre pressure, which are equally important for safe and efficient driving.
By taking a proactive approach to vehicle maintenance and following the guidance in this comprehensive guide, you’ll be well-equipped to keep your car running smoothly and safely. For more helpful motoring advice and maintenance tips, explore our other guides on keeping your vehicle in good condition and recognising when professional attention is needed.
