Keeping your car’s engine well-lubricated is vital for smooth performance and longevity. Choosing the correct engine oil not only protects your engine from wear and tear but also helps it run efficiently under different temperatures and driving conditions. 

In this guide, we’ll explain everything you need to know about selecting the right oil, checking car oil type, and topping up your engine safely.

 

Why is engine oil so important for your car?

Engine oil is the lifeblood of your car’s engine. Its main roles include:

  • Lubrication: Reduces friction between moving parts to prevent wear.

  • Cooling: Helps distribute heat evenly to avoid overheating.

  • Cleaning: Many oils contain additives that remove sludge and deposits.

  • Protection: Prevents corrosion and optimises sealing for efficiency.

Using the correct oil ensures your engine operates smoothly and extends its lifespan.

 

What is viscosity in relation to oil?

Viscosity in relation to engine oil refers to how easily it pours at certain temperatures.

A thin oil is one that has a lower viscosity, pouring more easily at lower temperatures than thicker oils, which have a higher viscosity.

Thin oils: minimise engine friction and help ensure it can start in cold temperatures.

Thick oils: More effective at maintaining film strength and oil pressure at high temperatures and under heavy loads.

 

Understanding Oil Viscosity

Viscosity describes how easily an oil flows at a given temperature.

  • Thin oils (low viscosity): Flow easily in cold conditions, reducing friction and helping the engine start in winter.

  • Thick oils (high viscosity): Maintain pressure and protective film strength at high temperatures or under heavy loads.

How Oils Are Labelled

Engine oils are labelled using a XW-XX system:

Label

Meaning

Use

5W-30

5 = viscosity in cold (winter) temperatures; 30 = viscosity at 100°C

Suitable for colder climates and moderate driving conditions

10W-40

10 = cold temperature viscosity; 40 = hot temperature viscosity

Ideal for warmer climates or older engines

0W-20

0 = excellent cold flow; 20 = thinner at high temperature

Common in newer, fuel-efficient vehicles

Lower W numbers are better for cold climates, while higher second numbers suit hot climates or summer driving.

 

How to check your car’s oil type?

Vehicle handbook

Your handbook will detail which oil is required for your vehicle.

 

Check online

If you've lost your handbook, there are a number of online resources you can use to find out which oil you need for your car, such as the Castrol oil checker (see list below).

Simply enter the make, model and variant of your car to find out what type of oil you need.

Some search engines may also ask other details, such as how frequently you drive your car.

 

Why is it important to buy the right oil for your car?

Your car's engine was designed to be used with a specific type of oil.

This specification of oil will help keep your engine running well for as long as possible, so it’s important to use the right oil for your car.

 

Resources for finding out which oil you need for your car

If you cannot locate your handbook, you may be able to find a digital version online. However, it is probably easier to use an online resource to find out which oil you need for your car, such as those listed below:

 

https://www.total.co.uk/lub-advisor

https://www.halfords.com/motoring/engine-oils-fluids/engine-oil

https://www.eurocarparts.com/engine-oils

https://www.castrol.com/en_gb/united-kingdom/home/car-engine-oil-and-fluids/motor-oil-and-fluids-finder.html

 

How to Check and Top Up Engine Oil

Checking Your Car Engine Oil

  1. Park on level ground with the engine off and cooled.

  2. Open the bonnet and pull out the dipstick. Wipe it clean.

  3. Re-insert the dipstick fully, then remove it again to check the oil level.

  4. The oil should be between the min and max marks.

Regularly checking engine oil ensures your car is protected from damage caused by low or dirty oil.

 

Topping Up Your Car Oil

  1. Locate the oil filler cap (marked with an oil can).

  2. Add a small amount of oil at a time, rechecking the dipstick after each pour.

  3. Stop when the oil reaches the max mark.

  4. Replace the cap securely and reinsert the dipstick.

Always top up gradually to avoid overfilling, which can harm your engine.

 

How much oil does my car need?

The amount of oil your car needs depends on the make, model, and year of your vehicle.

The easiest way of finding out how much your car needs is to read the owner’s manual.

If you are simply topping up your car’s current oil, put a little in at a time, re-checking the dipstick as you go. 

 

How to put oil in the car

  1. Look for the oil filler cap (marked with an oil can). It should be located near the engine and dipstick.
  2. Top up the oil tank with a little oil, doing so slowly and carefully.
  3. Each time you put a little more oil in, re-check the dipstick. Get the oil level as close to the ‘max' mark without going over it.
  4. When finished, screw the oil cap back on securely; re-insert the dipstick.

 

Keep Your Engine Healthy

Regularly checking and maintaining the correct engine oil protects your car from unexpected breakdowns. If you want complete peace of mind while on the road, consider getting breakdown cover today to keep your vehicle and your journeys fully protected.