If you don't know what engine oil your car needs, it's very easy to make the wrong choice. There are plenty of options available, and it can be overwhelming if you don't know what to look out for. Unfortunately, the wrong decision can cause severe engine damage - so you need to choose the right oil! That's why we're here to help.

By the end of this article, you will know:

  1. What the oil grades mean
  2. How to find which oil your car needs
  3. The differences between semi-synthetic, fully synthetic and mineral oils
  4. How long oil lasts
  5. How to change engine oil

Summary

There's nothing more important than choosing the right engine oil for your car. Your engine is designed to use a specific oil grade and viscosity and a certain type of oil. Most modern cars use a multigrade, semi-synthetic oil, whereas older cars are designed to use mineral oils. You can identify a multigrade oil by checking if it has numbers either side of the 'W'. Engine oil should last 5,000 miles between oil changes, and you must change the oil and oil filter together. Else, your oil will be less effective and will need changing more frequently.

 

shelf of motor engine oil in auto shop

There's plenty of choice when it comes to engine oil - possibly too much choice if you don't know what the grades mean! Photo by Robert Laursoo on Unsplash

 

What Type of Engine Oil Does My Car Need?

Most modern cars use semi-synthetic oil. They can run on fully synthetic and mineral oils, but there are plenty of disadvantages to doing so.

Drivers of older vehicles will need to use mineral oils. These can still provide high-quality lubrication despite their issues, especially in classic cars. Many manufacturers and mechanics recommend only using mineral oils in these vehicles. That's because each engine is designed to run a specific oil grade and viscosity.

Unless your vehicle is heavily performance modified, you should NOT stray from the recommended grade and viscosity of oil. This may mean that you have to pay a little extra, or change oil more often, but also get the full performance from your car.  

What Does Engine Oil Do?

Oil lubricates the moving parts in your vehicle's engine. Combustion generates high levels of heat and friction which oil helps to negate. The metal would smash and grind together as it powered your car if the engine ran dry. In essence, your car wouldn't run without oil. So if you don't change your oil regularly, or use the wrong type of oil, you can face a hefty repair bill.

Types of Engine Oils

Making sense of the names of different kinds of motor oils can be overwhelming to begin with. 5w40, 15w30, 0W30, 10W60 - what does any of that mean? An oil with numbers either side of the 'W' is known as multigrade oil. These can cope with seasonal temperature variations. Most of us need multigrade oils and they are the most common type of engine oil. That's because they offer a cost-effective way to keep your car running no matter the temperature.

An oil that only has a number in front of the 'W', or no 'W' at all, is known as a monograde oil. Below is an explanation of what the numbers on a multigrade oil marked '5W40' mean:  

5 = Viscosity grade at low temperatures. This is how easily the oil flows through your engine. The lower the number, the easier the oil flows; the higher the number, the thicker the oil. Thicker oil forms a protective film across engine parts.

W = 'winter'. Engine oils marked with a 'W' are more fluid at colder temperatures. This makes your car easier to start during winter. If the oil is not marked with a 'W', it's designed to work better in warmer months.

40 = Viscosity grade at high temperatures. A high grade means that the engine is properly protected in warm weather but won't be as fuel-efficient. A lower number makes the oil more effective at reducing friction and saving you money at the pump.  

So, that's the numbers explained. However, there's still the small matter of working out which type of engine oil your car needs. Your options are fully synthetic, semi-synthetic and mineral - but what are the differences? 

What is Mineral Oil?

Mineral oils are refined crude oil. The refining process removes contaminants, unwanted hydrocarbons, and other unnecessary natural gunk. Mineral oil has been around a lot longer than synthetic oils and, being a lot less refined, isn't great for modern cars. They flow through your engine slower than synthetic oils, need to be changed more frequently and increase your fuel consumption - none of which is ideal. This type of oil is better suited to older vehicles.

What is Fully Synthetic Oil?

Fully synthetic oil is a highly refined, chemically modified performance oil. It has fewer impurities than mineral oils and includes plenty of additives to boost its lubricating power. Fully synthetic oil is way more efficient than mineral oil. It also offers plenty of advantages, which include:

  1. Less frequent need to change
  2. Less wear on engine parts
  3. Increase engine lifespan

Unfortunately, this does come at a cost. Fully synthetic oil is more expensive than mineral oils.

What is Semi-Synthetic Oil?

Semi-synthetic oil sits between the two. The formula isn't as advanced as fully synthetic oil but is still more refined than mineral oil. This means that semi-synthetic oil is a cost-effective option for many drivers.

 

 

How Do I Find Out What Oil My Car Takes?

The best place to find out what oil your car takes is to consult the vehicle handbook – the document which comes with every new vehicle. Inside you will find the viscosity and type that the manufacturer recommends for your vehicle.

Some manufacturers develop their own oil specifications. These include VW, Mercedes, BMW, and GM. If your vehicle handbook recommends manufacturer's specification oil, you MUST buy an oil that satisfies this. Specialist oil can cost a little extra, but they are 'long life' oils, designed to support long intervals between services. This saves you money in the long run - which is always handy!

It also may suggest the best alternatives if you can’t get hold of your usual oil, and what to use during different seasons. If you don’t have the vehicle handbook or have misplaced it (it’s easy to do!), pop the bonnet – some manufacturers list it on the oil cap or on a sticker on the inside of the bonnet. If not, you can check with the dealership or your local mechanic.

Sometimes the oil sections in parts stores have charts you can consult there – but this can be confusing. If in doubt, contact a professional. You can also enter your make and model into an online tool, such as Opie Oils.

If you are still unsure about what oil your car takes, book an appointment with a local garage today. They can help explain which oil suits your needs.

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At this point, we hope you’ve worked out what type of oil you need. What you might not know is why choosing the right oil is so important. After all, surely you can mix two different types of oil if the alternative is driving without engine oil at all?

Can I Mix Two Different Oils?

Mixing two different brands of engine oils will not cause any immediate issues. However, it is best to just keep to the same brand of oil each time. Even oils with the same viscosities have different chemical compounds, so it could be dangerous mixing unknown chemicals together. It could even result in engine damage.

It is risky to mix two different viscosities. Again, you don’t know what each oil is made up of, and how the ingredients will act when mixed.

If you get caught short and need to top up with a different brand of oil, as long as the viscosities are the same, you’ll manage to reach your destination. If you find yourself in this situation, we recommend that you change your oil as soon as you can.

Will The Wrong Oil Damage My Engine?

If you make a mistake and put the incorrect oil in your vehicle, it isn’t the end of your car’s life – right now. However, doing so can cause problems further down the line. If you realise that you’ve put the wrong oil in your car, it’s best to have it changed. You can learn how to do this below.

If you unknowingly have been using the wrong engine oil for a while, your car will let you know. If the viscosity is wrong, you may end up with an oil leak due to the different flow properties. You might also be able to smell burning – this is because different oils heat at different temperatures. This could result in your engine not lubricating itself properly, which will lead to much larger issues in the future.

Using the incorrect motor oils will not cause you immediate issues, but to keep your car at peak performance it is strongly advised that you identify the best oil to use and stick with it.

If you think you might have been using the wrong oil and it has potentially caused some damage, don’t hesitate to book an appointment with a local garage so they can have a look. We can get you in touch with a trustworthy mechanic who can help you decide which steps you should take next.

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How to Change Engine Oil

   

If you check your oil (see above) and realise it needs changing, here's how you can do it yourself.

  1. Remove the sump plug and drain oil. You can find this on the underside of your car (so you will need to raise it off the ground).
  2. Replace the sump plug once all the oil has drained.
  3. Refill the oil to the correct level. Following the manufacturer recommendations for grade, type and quantity of course.

  However, an oil change on its own isn't very helpful. Oil flows through an oil filter, which catches any debris, dust or bits of metal oil has picked up while moving through the engine. As a result, this filter gets dirty very quickly. If you don't change your oil and oil filter together, your oil will become less effective much sooner! This can lead to problems in the future, including increased fuel consumption and more frequent oil changes. If you can't change your oil and oil filter together, book an oil and filter change at a garage near you and get a professional to do it for you.

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How Much Oil Does My Car Take?

The amount of engine oil your car needs can range from 3 litres all the way up to 12 litres. Generally, the larger the engine, the more oil your car needs.  

Engine Size

0-1200cc

1201-1500cc

1501-2000cc

2001-2400cc

2401-3500cc

3500cc+

Average quantity of oil used in an Oil and Filter Change

3.5 litres

4.9 litres

5.2 litres

6.1 litres

6.4 litres

8.1 litres

If you choose a professional mechanic to complete your oil change, they will have access to the exact amount of oil your car needs. This saves you any extra stress that over or underfilling your engine oil can cause.

How Long Does Engine Oil Last?

Most manufacturers recommend an engine oil change every 5,000 miles for modern cars. If your car runs on older mineral oils, this may be as often as every 3,000 miles but for fully synthetic oils, you could drive 10,000 miles between oil changes. The BookMyGarage service schedule always includes an oil change as standard. This includes a full drain and refill of your engine oil, as well as a fresh oil filter. When you book a service with one of our UK garages, you can rest assured that your car gets the right oil, as well as the full amount it needs.

Engine oil must be golden in colour to provide maximum effectiveness. If you notice that yours is dark brown in colour or full of lumps, you need to book an oil change as soon as possible.

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fresh golden engine oil being poured from green bottle into car oil tank

Engine oil must be golden in colour to provide maximum effectiveness. If you notice that yours is dark brown in colour or full of lumps, you need to book an oil change as soon as possible.

 

Recap

There's nothing more important than choosing the right engine oil for your car. Your engine is designed to use a specific oil grade and viscosity and a certain type of oil. Most modern cars use a multigrade, semi-synthetic oil, whereas older cars are designed to use mineral oils. You can identify a multigrade oil by checking if it has numbers either side of the 'W'. Engine oil should last 5,000 miles between oil changes, and you must change the oil and oil filter together. Else, your oil will be less effective and need changing more frequently. You can book a professional oil change with one of thousands of UK garages here.