What engine oil for my car?

Wondering which motor oil to choose for your car? Like many motorists, you feel lost when it comes to finding the right oil for your engine. And that’s normal: without a minimum of explanation, it’s hard to understand what makes a particular motor oil different and why it’s best suited to your vehicle. Here’s our advice on how to make the best choice!

Engine oil: what does it do?

Engine oil is essential to the smooth running of your engine, for a number of reasons:

• It helps to lubricate the metal parts located in the engine: in this way, the engine oil limits the friction between these parts, and therefore their overheating. As a result, they wear out less quickly.
• It helps keep the engine sealed: thanks to it, the combustion chamber is protected against moisture and corrosion.
• It contributes to the cooling of the engine: by continuously circulating in the engine, the oil removes some of the heat generated by combustion and friction.
• It cleans the engine: thanks to its constant movement, it carries the impurities from combustion to the oil filter, which retains the largest particles.

Choosing the right oil for your vehicle is essential to avoid premature wear on the engine and its components.

Which engine oil for my car: main criteria

To choose your engine oil, you’ll base your choice on several criteria :

1. The recommendations given in your vehicle’s service booklet
2. Motorising your vehicle
3. Type of engine oil
4. Viscosity index
5. Standards
6. The brand.

1. Recommendations in the maintenance booklet

To find the most suitable motor oil for your car (or another type of vehicle), you’ll rely primarily on the manufacturer’s recommendations. To do this, go to the lubricants or engine oil section of your vehicle’s operating manual. You’ll generally find recommendations on: recommended types of oil and viscosity indexes, manufacturer standards, or warnings (e.g. prohibition on using oil additives).

2. Your vehicle’s engine

While there are many oil references that are suitable for both diesel and petrol engines, some are only compatible with one type of fuel. So be careful to select the right oil for your engine. What’s more, if your vehicle is fitted with a particulate filter, be aware that you’ll need to opt for an oil that is suitable for this type of equipment.

DPF filter cleaning: effectice methods and costs

3. Type of engine oil

The choice of engine oil type will firstly be based on what is recommended by your manufacturer in the user manual. In general, manufacturers indicate one or more types of oil to be preferred to meet their performance, fuel economy or engine protection requirements.

While there are several choices available, you’ll need to take into account the climate of the geographical area where you live, your driving style, or the typology of your journeys to select the oil that’s right for you.

There are three main types of motor oil:

• Mineral oils: obtained from crude oil, these are recommended for older vehicles (over 12 years old) or those with many kilometres on the clock.
• Synthetic oils: chemically designed, they offer greater stability and superior performance than other oils. They are particularly suited to difficult climatic conditions (cold and rain) and to vehicles on the road every day, both on roads and motorways. In addition, the additives contained in synthetic oils enable them to reduce fuel consumption, ensure longer engine life and limit pollutant emissions.
• Semi-synthetic oils: made up of a mixture of mineral oil and synthetic oil, they are suitable for vehicles that drive mainly in town or for motorists with a flexible driving style. They offer good value for money.

4. Viscosity index

The viscosity index measures the speed at which the oil will flow as a function of a defined temperature. This is an essential element to take into account when choosing an engine oil, as it will have a direct impact on engine operation.

According to the SAE (Society of Automative Engineers) standard, the viscosity index takes the following form:

• a first number, which specifies the grade of winter or cold viscosity, followed by the letter W (for Winter): the closer this number is to zero, the more liquid the oil will be when cold, and the easier it will be to start the engine at low temperatures
• a second number, which indicates the viscosity grade in summer or hot weather: the higher this number, the thicker the oil will be at high temperatures, and the more protected the engine will be at high temperatures. Conversely, a lower grade will further limit friction between parts and reduce fuel consumption.

To find out which viscosity index(es) are recommended for your vehicle and which engine oil to choose, consult its owner’s manual. If several viscosity indexes are indicated, choose the one that best suits your situation. You can also enter your number plate on Amazon, and you’ll get a list of oils suitable for your vehicle’s engine.

Here is a comparative table of motor oils according to their viscosity:

Elements	0W30 engine oil	5W30 engine oil	5W40 engine oil	10W40 engine oil	15W40 engine oil
Type of engine oil	Synthetic	Synthetic	Synthetic	Semi-synthetic	Mineral
Cold start	★★★★★	★★★★	★★★★	★★★	★★
High temperature resistance	★★★★	★★★★	★★★★★	★★★★	★★★★
Fuel economy	★★★★★	★★★★★	★★★	★★
Oil change intervals	★★★★★	★★★★★	★★★★★	★★★★	★★★
Adapted to particulate filters (DPF)	Yes	Yes	No	No	No
Types of journey	City, road, motorway	City, road, motorway	City, road, motorway	City, road	Road
Special features	Suitable for extreme winter temperatures	Recommended for recent vehicles with DPF	Recommended for recent vehicles without DPF	Good performance/price ratio	Suitable for older vehicles (> 12 years)

Notes :

• Motor oils of the same viscosity are miscible with each other. In other words, they can be mixed together, whatever their brand or origin, as long as they are compatible with the manufacturer’s requirements.
• on the other hand, a 5W30 oil can only be replaced by a 5W40 oil (and vice versa) if the vehicle make explicitly states this in the service manual.
• brands of diesel vehicles fitted with SCR systems (running on AdBlue) generally recommend the use of 5W30 engine oil.

What’s the difference between 5w30 and 5w40 engine oil?

5. Standards

Mentioned on the label of motor oil cans, the standards take the form of combinations of numbers and letters. They enable you to check the characteristics of the oil in question: engine type and performance level. Refer to your vehicle’s service manual for the standards recommended by your manufacturer.

There are two main classifications:

• the ACEA standard (Association des Constructeurs Européens d’Automobile), which works as follows:
  • the letter specifies the type of fuel used: A for Petrol and B for Diesel
  • the number on the right specifies the performance level: from 1 (for standard quality, with fuel savings) to 5 (for high quality, with fuel savings)

• the API (American Petroleum Institute) standard, with the following operation:
  • the letter on the left indicates the type of engine: S for Petrol and C for Diesel
  • the letter on the right indicates the performance level: A (low level), J (high level – Petrol) or F (high level – Diesel).

6. The brand of engine oil

Now that you know which motor oil is right for your vehicle, it’s time to choose the brand of your can. Between Castrol, Elf, Motul, TotalEnergies, Liqui Moly, or private labels, you’re spoilt for choice!

Generally, manufacturers recommend a brand of engine oil in the service manual. You can simply follow this recommendation, but you are under no obligation to do so. In fact, as long as you respect the characteristics of the engine oil mentioned in the maintenance booklet, you are free to choose any reference that corresponds to them.

For example, Peugeot recommends using Total Quartz Ineo ECS 5W30 oil for the majority of its recent vehicles. This high-quality oil is particularly well suited to recent diesel and petrol vehicles fitted with particulate filters. It also helps to save fuel when starting the vehicle and limits CO2 emissions.

What makes the difference between a lambda motor oil and a branded oil is generally the additives that are added by the brands to make their oil perform better.

To sum up: what engine oil for my car?

There are several ways to choose a motor oil for your car:

• Do you have your vehicle’s owner’s manual? It will clearly tell you what type of oil to use (viscosity index, standards to be met, recommended brand, etc.).
• Get your car’s number plate from a site like Amazon. The site’s engine will present you with a list of oils compatible with your car’s engine.
• Contact your car dealer or garage: they’ll be able to tell you which oil to buy for your vehicle.

How much engine oil should I buy?

The quantity of motor oil to buy depends on what you plan to do with it:

• If it’s a question of an change, first follow the recommendations given in the service manual to find out how much engine oil is needed for your vehicle. On average, you need to add 4 litres of oil after an oil change. So bring along a 4 to 5 litre can.
• In the case of a fill to top up the oil (particularly if the engine oil warning light is displayed on your dashboard), a 1-litre can should suffice. In fact, it’s a good idea to keep a 1-litre can of oil on hand at all times, just in case the unexpected happens.

If you wish, you can add to your knowledge of motor oil on the dedicated Wikipedia page.