Which engine oil for my car?

Why do I need to check my oil level?

Oil has a pretty important job to do in your car’s engine. It acts as a lubricant, and has a cooling effect, making sure your engine doesn’t overheat as it passes through. Small amounts of soot and dirt tend to build up in engines as well, and oil contains detergents that dissolve this dirt before it becomes a problem.

If there isn’t enough oil in your engine, the oil can overheat and degrade. This makes it less effective at lubrication and cooling, and can lead to low oil pressure. Low oil pressure can mean increased wear on your engine. You need to keep an eye on your oil level to make sure it doesn’t drop too low and potentially cause you problems.

If you’d like to learn more about how your engine works, you can check out our blog ‘Do diesel cars have spark plugs?’

When should I check my oil level?

All car engines consume a small amount of oil when running, even if they’re in great condition. It’s nothing to worry about, but it’s worth checking your oil level regularly to make sure you’ve got enough to keep you going. It’s recommended to check your car’s oil level at least once a month, if not every couple of weeks, as well as before long journeys.

What engine oil does my car need?

Different engine oils have different viscosities (thicknesses), operate effectively at different temperatures, and be better suited to either diesel or petrol engines. There are all sorts of tables you can look at to find the perfect oil for your car, but these are the simplest ways to check exactly what kind of oil your car needs:

• Check your handbook - The simplest way to find out what oil your car needs is to check your car’s handbook. It should list all the specifications and grades of engine oil that will work for your car.
• Search tools -  There are a lot of online search tools that can help you find the right oil for your car. Euro car parts and Castrol both allow you to search your registration number or your car’s make and model and will provide you with options.
• Talk to a professional - If you have a particularly specialist car, or your handbook lists a number of very specific options, you might want to talk to a mechanic that’s approved by your manufacturer to see if they have an oil they prefer to use.

If you drive a diesel car with a DPF (diesel particulate filter) you’re generally recommended to use a 'low SAPS' (Sulphated Ash, Phosphorous, Sulphur) oil. Using 'normal' oil instead of low SAPS can block your DPF, because too many particles will build up in the filter.

There are a couple of types of oil, classified as 5W30 and 5W40, that are the most common and tend to be compatible with common car models like a VW Golf or a Ford Focus. The ‘5W’ notes the viscosity of the oil in cold weather. The ‘30’ and ‘40’ tell you the oil flow at high temperatures. Newer petrol engines tend to be better suited for 30, whereas older petrol engines and diesel cars tend to use 40. It’s still best to do your homework rather than just going straight for these, but they may help you with getting a hang of the naming systems.

For more information on what you should be putting in your car, you can check out our blog ‘Is my car compatible with E10 fuel?’

How much engine oil does my car need?

Too much oil in your car can cause as many problems as too little, so it’s important to get the right amount. This is how you can make sure you’ve got the right amount of oil in your tank:

• Check your handbook - Your car’s handbook should come with all the information you need to check exactly how much oil your car needs.
• Online tools - As well as telling you what kind of oil you need, online search tools should be able to tell you how much you need for your engine to run perfectly.
• Talk to a professional - If you’re topping up your oil, it can be hard to know exactly how much to add so you don’t overfill your tank. Asking a mechanic who specialises is a simple way to make sure you’re adding the right amount.
• Estimate based on engine size - If you’re in the shop and trying to figure out how much oil you need to buy, you can estimate based on the size of your engine. This isn’t a guide for how much to add, just how much you might need altogether. It’s best to find an exact amount using the options above.
  • Four-cylinder engines tend to need around 3.5 to 4.5 litres
  • Six-cylinder engines tend to need around 4.5 to 5.5 litres
  • Eight-cylinder engines tend to need around 5.5 to 7.5 litres

Can I put engine oil in a hot car?

If your oil level light came on whilst you were driving and you want to top up your oil when you get home, it’s not uncommon to be a bit concerned about adding oil to a hot engine. There is actually not considered to be much danger in adding oil to a hot engine, because oil absorbs heat much slower than water. This means the temperature won’t change dramatically and damage your engine when you add in your oil.

It is important to take care when doing any work on an engine that is still hot.. wearing gloves or waiting for your engine to cool for 30 minutes before you work on it could be a great option if you’d prefer to be on the safe side

If you’re looking to answer more technical questions, check out our blog ‘Can you put diesel in a petrol car?’

A few final tips…

Here are the last couple of things to remember when checking which oil to put in your car:

• Oil expands when it’s hot, so it’s important to be careful that you are not overfilling your tank. If you are adding oil when the engine is cold, it’s best to be cautious, adding a little at a time and doing your best not to overfill.
• Your car’s handbook or owner’s manual are your best friend when it comes to checking the type of oil and how much you need. They’ll often provide you with a few different options so you can find one that works for you.

Urban Jungle is not a financial advisor and information in this article should not be taken as advice or recommendation.