The world of oil: how, what and why

Bardahl engine oil is available in many types, including mineral and synthetic oil, as well as a range of viscosities and packaging formats. Whichever type you buy, Bardahl engine oil always provides exceptionally good lubrication for your car, motorcycle, scooter, tractor, kart and more.

For many people, oil is an abstract subject that raises numerous questions. Why is it important to change the oil, and which oil is right? These 10 questions and answers introduce you to the world of oil.

1. What exactly does engine oil do?

The main tasks of oil are:
• Engine oil provides a seal between pistons and cylinders
• Engine oil prevents contact between different moving parts
• Engine oil carries away heat produced by combustion
• Engine oil collects and carries away combustion residues and wear particles.

2. How can I recognise the quality of engine oil?

Engine oil quality is indicated by international API and ACEA standards and by vehicle manufacturer standards.

3. What does API mean?

API stands for American Petroleum Institute, an American organisation that specifies oil quality. API distinguishes between petrol and diesel engines.
• Petrol engines are identified by the letter S.
• Diesel engines are identified by the letter C.
A second letter indicates the quality level. With a few exceptions, the further along the alphabet, the higher the quality. For example, an engine oil may have the SL/CF quality classification.

4. What does ACEA mean for engine oil?

The ACEA is a European standard and stands for Association des Constructeurs Europeens d’Automobile, or the European Automobile Manufacturers' Association. The ACEA quality classification consists of a letter followed by a number.

ACEA distinguishes between petrol engines, identified by A; light-duty diesel engines, identified by B; diesel engines with a diesel particulate filter, identified by C; and heavy-duty diesel engines, identified by E.
A number after the letter indicates the quality level. For example, an engine oil may meet the A3, B4 and C3 specifications.

5. Which oil does my car need?

Your car's handbook specifies which type of oil, meaning which specification, the engine or gearbox requires. Always choose a quality oil brand.

The conditions in which engine oil works over an average year can vary considerably: temperatures from + 30°C to -10°C, short journeys in town and long holiday journeys, commuting and driving through the mountains with a heavily loaded car and caravan.

Engine oil is now sold in many places, from petrol stations and garages to DIY shops and supermarkets. Remember that oil has many tasks to perform while it is in your car, under widely varying conditions. Its tasks are described above.

The designation 5W30 only indicates viscosity. Specifications such as SM/CF or SN/CF tell you about the oil's quality level, and there can be substantial differences. Bear in mind that the conditions in which oil must work are varied and demanding, as described above.

You will see which engine oil is suitable for your car. You will also see the recommended brake fluid, transmission oil and coolant.

‘Cheap engine oil can prove expensive in the long run.’

You can see why 5W30 oils developed by reputable brands to the latest specifications have a long, stable service life. They are therefore well suited to the demanding conditions cars encounter. This contrasts with a 5W30 oil marketed as cheap engine oil to attract customers, meeting only minimum specifications with a minimal additive package.

An engine's mechanical components can last a long time, provided that engine oil is changed on time and the oil meets the prescribed specifications.

To sum up: 5W30 oil is sold in many places, but one 5W30 oil is not the same as another.

6. What is viscosity, and how can I recognise it in an engine oil?

The thickness of engine oil is an important property. It is expressed as viscosity, which depends on temperature. Low-viscosity oil is thin, while high-viscosity oil is thick. SAE (Society of Automotive Engineers) is the international organisation that established the engine oil viscosity standard. Engine oil viscosity is specified at low and high temperatures, giving designations such as SAE: 5W30 oil, 10W40 oil and 5W40 oil.

The first number, followed by W: the lower the number, the thinner the oil at low temperatures, which matters during cold starts. The most common are SAE: 0W, 5W, 10W, 15W, 20W.

The second number, after W: the higher the number, the thicker the oil remains at high engine temperatures, which matters in summer. The most commonly used are SAE: 30, 40 and 50. As a general rule, the higher the SAE number, the higher the viscosity.

7. What are the advantages of synthetic engine oil?

Synthetic engine oil offers several advantages over mineral oil:
• Synthetic engine oil has lower resistance, resulting in lower fuel consumption. Better fuel economy saves money, and lower fuel consumption is also better for the environment.
• Synthetic engine oil is thinner, so it circulates through the engine more quickly, even during cold starts. This rapid lubrication greatly reduces engine wear.
• Synthetic engine oil has more stable thermal properties than mineral oil. This means it can withstand heavy loads better and for longer, allowing longer oil change intervals. When should you change your oil? This depends on the car and engine type. Your handbook specifies the oil change interval.

8. When should I top up the oil?

Use the dipstick to check whether there is enough engine oil to provide sufficient lubrication. Note that the difference between the minimum and maximum levels is 1 litre. Check your oil level regularly: by the time the oil warning light comes on, you are already too late!

P.S. If you drive a company car, you are responsible for its oil level.

It is advisable to keep a 1-litre pack of the correct engine oil for your car in the vehicle. If the oil warning light comes on, you can top up the oil and continue. Continuing to drive with a low oil level can cause permanent engine damage.

9. Is topping up with another brand of oil harmful?

In principle, no, provided the other oil has the same quality level, meaning the same specifications, and preferably the same viscosity. In emergencies, such as a low oil level, it is important to top up to prevent permanent engine damage. However, always use oil that meets the manufacturer's minimum required specifications to avoid damage. If in doubt, consult your vehicle's handbook or a specialist.

10. What if my vehicle has a particulate filter?

For cars fitted with particulate filters, using the correct engine oil is very important. Oil without the right specifications causes significantly more contamination, including soot, and faster clogging of the particulate filter. Contamination harms the engine and particulate filter, as well as the turbo, which is very sensitive to it.
The engine oil you need depends on your engine type. Bardahl offers a range of engine oils suitable for particulate filters.

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Did you know that 25% of engines have a low oil level?

Use the dipstick to check whether there is enough oil in the engine. Note that the difference between the minimum and maximum levels is only 1 litre. Check your oil level regularly, for example every month. By the time the oil warning light comes on, you are already too late!

How can I easily check my oil level?

1. Always check the level when the engine oil is cold. The oil will then be fully in the sump, allowing you to measure exactly how much engine oil needs to be added.

2. Make sure the car is on level ground.

3. Pull out the dipstick. If you cannot find it, your handbook shows its location.

4. Clean the dipstick with a cloth or paper towel and fully reinsert it.

5. Pull the dipstick all the way out again and check how far the oil reaches. The dipstick has either level marks or min–max markings.

6. If the oil does not reach max., top it up to max.

‘Never fill above the MAX mark!’

It is advisable to keep a 1-litre pack of the correct Bardahl engine oil for your car in the vehicle. If the oil warning light comes on, you can top up and continue. Continuing to drive with a low oil level can cause permanent engine damage!

‘What if the oil warning light still comes on?’

Stop the car as soon as possible and immediately top up with the correct engine oil. Then drive to the first petrol station or garage and check the level again to see how much oil actually needs to be added. Let the engine cool first so that all the oil has drained into the sump. Only then can you measure the level accurately.

Changing engine oil?

We regularly hear the question: “I do not drive many kilometres, so is it true that I do not need to change my engine oil?”

Unfortunately, the opposite is true. If you drive few kilometres and your car often stands unused, for example a classic car using mineral oil, it is particularly important to change the engine oil at regular intervals of 1 year. Several serious problems can arise if you overlook oil ageing.

Sludge is yellowish and resembles white mayonnaise. It forms when oil in the engine becomes contaminated. It is quite common in the sump, where piston movement repeatedly draws air in and pushes it out.

‘Sludge forms when water or moisture mixes with engine oil.’

Sludge can form because piston movement continually changes the volume, drawing air into the sump and pushing it out again. Moisture in that air causes condensation. It mixes with the oil and forms white sludge. Sludge forms when water or moisture mixes with engine oil. Condensation is particularly common when a car makes many short journeys.

An unfortunate consequence of sludge is that oil containing too much moisture oxidises and oil additives can turn into acids. These acids can attack metal, while moisture can cause oxidation and rust. Eventually, the oil's cleaning and lubricating effect decreases sharply. Wear can then follow quickly, with all the resulting consequences.

‘Changing oil too late can lead to increased oil consumption.’

Your car's service handbook is the first place to check how often the oil should be changed. Take this seriously. Changing engine oil too late can cause problems such as increased oil consumption and adverse effects on the turbo, EGR and particulate filter. The oil's cleaning effect decreases as it becomes saturated, with all the consequences this entails. It is better to change the oil a little early than too late.

‘Summary’

Engine oil changed too late contains too much moisture, while the additives become less effective.

This leads to additional wear and oxidation.

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