The role of engine oil is to coat the components of the engine in lubricant, reducing friction where these parts interact. This prevents wear, reduces emissions, maximises engine performance and improves the lifespan of critical engine parts - provided you choose the right product for the job.

There are many things to consider when shopping for engine oil, ranging from the technical specifications of your vehicle to the driving conditions in which you use it, and the products your vehicle's manufacturer recommends. Whether or not you have a strong knowledge of the technical specifications you need, there are so many products available on the market that it can be overwhelming to determine which one is the right choice - or even to understand the differences between the products on the market.

Castrol's EDGE range has a number of products engineered in conjunction with vehicle manufacturers and specifically developed for their applications. While this is often a good place to start shopping, it can also help to understand the technical specifications that determine whether or not a product is suitable for your needs.

Here, the knowledgeable technical team at Broughton Lubricants breaks down what you need to know about shopping for engine oils, including the specifications that apply, the differences between some of the most common products, and where you can go for more information.

To discuss your application in detail, you can also get in touch with our automotive experts by calling 03300 555 109 or using our online enquiry form to send a message.

Grade

Every oil product has a grade, which acts as a guide to its viscosity. Often, a lubricant's grade will be included in the name of the product: for example, Castrol EDGE 5W-30. There are many different levels of viscosity available, but the grade will always take a form like 5W-30, 0W-40, or 10W-60. It is important to choose a product with the right technical specifications for your vehicle, to benefit from the best possible engine performance.

As the temperature of the operating environment changes, the oil in your engine will become thicker or thinner. Grades of viscosity are used to quantify this by assigning a number system, with the lower number indicating a lower viscosity, and the higher number indicating a higher viscosity.

The first number in the rating indicates the oil's viscosity in cold temperatures. The 'W' stands for winter, and the lower the number, the easier the oil flows in cold temperatures. For example, 5W-30 has a lower cold temperature viscosity than 10W-50, which means it can flow more easily in cold conditions. This is important because it allows the oil to circulate more quickly when you start your car in cold weather, reducing engine wear.

The second number in the rating indicates the oil's viscosity at high temperatures. The higher the number, the thicker the oil, and the better it can protect the engine at high temperatures. In this example, 10W-50 has a higher viscosity than 5W-30, making it more suitable for high-performance engines that operate at extreme temperatures.

However, it may not be suitable for colder climates or older engines, which require a thinner oil to circulate properly. Depending on the specifics of your application, you may require a grade like 0W-40, which is thin enough to flow quickly in cold temperatures but gets thicker to protect critical engine parts as the engine warms up.

You can consult your manufacturer's recommendation to learn what grade of oil you need, but the specifics of your application may demand different specifications if you are pursuing superior performance. For example, vehicles that drive in warm weather might require thicker grades than are recommended.

If you are unsure what grade you need or feel that you may require a different product than your manufacturer has recommended, we will explain the process you should follow to determine this below.

Additives

In addition to viscosity, engine oils can have a range of additive properties that benefit different vehicles and applications. There may be many products that will meet the minimum technical requirements you need from an engine oil, but each will have a different combination of additional properties that could have specific advantages for your vehicle. 

For example, some oils contain detergents that help to clean the engine of sludge and deposits. Others contain anti-wear additives that protect engine components from wear and tear. Some oils also have anti-foaming agents, which prevent bubbles from forming in the oil and reduce the risk of engine damage. Many of our engine oils are equipped with Castrol Magnatec technology, which is designed to add an extra layer of protection to engine components that are vulnerable to wear.

This is not only important for demanding applications - there is a wide variety of additives available and by researching the available options, you may be able to deliver superior performance from your engine.