Engine oil & coolant: how to check and top up safely

Regularly checking your engine oil and coolant level is one of the simplest and most important vehicle maintenance tasks. It helps prevent breakdowns, expensive repairs, and even MOT failures. In the UK, drivers are legally responsible for ensuring thier vehicle is roadworthy.

This guide explains how to check engine oil and coolant safely, spot common problems, and know when it’s time to see a mechanic.

Why oil and coolant matter

Your engine relies on two critical fluids:

• Engine oil lubricates moving parts, reduces friction, and helps regulate engine temperature.
• Coolant(antifreeze) prevents overheating and protects against corrosion and freezing.

• Engine overheating
• Oil pressure warning lights
• Internal engine damage
• Breakdown or MOT failure

Tools and safety prep

Before you start any engine oil check or coolant level check, gather the following:

• Clean rag or paper towel
• Correct engine oil
• Correct coolant/antifreeze mix
• Funnel

Safety first (best practice)

• Park on level ground
• Switch off the engine
• Let the engine cool for at least 10-15 minutes
• Never open the coolant cap on a hot engine

How to check engine oil

An engine oil check should be done at least once a month.

Step-by-step engine oil check

1. Open the bonnet and locate the oil dipstick
2. Pull it out and wipe it clean
3. Reinsert full, then pull it out again
4. Check the oil dipstick reading

Understanding the oil dipstick reading

• Oil should sit between the min and max marks
• Below min = low oil (top-up required)
• Above man = overfilled (can damage seals and cause oil leaks)

Signs of oil problems

• Oil pressure warning light on the dashboard
• Dark, gritty oil
• Oil leak under the car

If you spot an oil leak or a persistent warning light, stop driving and seek professional advice.

How to check coolant level

Coolant should be checked every few months and before long journeys.

Step-by-step coolant level check

1. Locate and coolant expansion tank (usually translucent)
2. Check the coolant level sits between the min and max markers

How to top up coolant safely

• Only top up coolant when the engine is cold
• Use the correct coolant type specified by the manufacturer
• Never use plain water long term (UK winters can cause freezing)

If you find yourself topping up coolant frequently, this may indicate a coolant leak.

Common faults and fixes

Low oil level

possible causes:

• Oil leak
• Worn piston rings
• Infrequent servicing

Fix – Top up oil short-term but book a service if it keeps dropping.

Coolant leak

Warnings signs:

• Sweet smell
• Puddles under the car
• Failing coolant level

Fix – Minor hose issues may be cheap, but a mechanic should handle full coolant leak repair.

Engine overheating

Causes:

• Low coolant
• Faulty thermostat
• Cooling fan failure

Action – Stop immediately and switch off the engine. Driving while overheating can destroy the engine.

White smoke from exhaust

What it may indicate:

• Coolant is leaking into the engine
• Potential head gasket failure

Action – Do not drive, seek urgent mechanical inspection.

When to see a mechanic

You should book professional help if you experience:

• Repeated oil pressure warnings
• Persistent oil and coolant leaks
• Engine overheating
• White smoke from the exhaust
• Rapid loss of coolant or oil

Final thoughts

Regular engine oil and coolant checks are quick and easy and can save you thousands in repair costs. Staying on top of these basics helps keep your vehicle safe, legal and reliable on UK roads.

If in doubt, always consult a qualified mechanic, especially when warning lights, leaks and overheating are involved.

If you like to learn more about car maintenance tips or driving advice check our our expert guides.