Car Engine Oil Explained: 4 Common Questions Answered

With grades, cleaning power, formulations and change intervals all to consider, engine oil is far more than the simple lubricant that you pour into your engine every time you get a service or need a top up.

Even if your car is relatively new and you take it to a dealer for servicing, you still need to check the oil level. And the older your engine, the more oil it will tend to use (or leak) and the more often you need to check the dipstick to make sure it stays above the minimum level. These are the most commonly asked questions about car engine oil.

What Does Engine Oil “Grade” Mean?

Using the right “grade” of engine oil for your vehicle is critical to ensure that your engine is properly maintained, kept clean and runs as smoothly as possible. But what do all the numbers mean, exactly?

In short, the numbers on your engine oil indicate the viscosity of the fluid at different temperatures. An engine oil with a lower grade, such as a 5W30 or a 0W40, is more viscous (thick) and therefore flows faster than a high-grade oil such as a 20W50.

What Does the “W” Stand for on the Engine Oil Label?

So then, what does the “W” in the middle stand for? Basically, the “W” stands for “winter”, meaning the viscosity of the oil in cold conditions. As engine oil heats up while the motor runs, it thins out. Engine Oils will also have a rating or specification that is listed on the bottle. Usually in the form of an ACEA rating. Your car service manual will specify a particular rating as a minimum and this should always be adhered to. Always purchase an oil with the rating specified by the manufacturer.

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How Do I Know When to Change Engine Oil?

Everyone knows what used oil looks like. It’s smelly, it’s black and it generally looks the polar opposite of the pure, nourishing looking amber liquid you originally poured into your oil tank at the last service interval. Often, even as little as a quarter or halfway through your service interval, a quick check of your dip stick will reveal the same darker substance that you’d normally associate with engine oil that needs changing. However, that’s simply not the case.

Modern engine oils are formulated with detergents and additives that clean your engine’s walls and linings from all the sludge, build ups and deposits that form naturally as your engine goes about its daily duties. Castrol Oil recommend that drivers check their vehicle manufacturer’s guidelines when determining when to change your engine oil.

Can I use a Fully-Synthetic oil in my everyday engine?

In a word, yes.

As the success of full-synthetic and semi-synthetic engine oils today would indicate, this of course is no longer the case, and the enhanced cleaning power of full-synthetic engine oil means it can actually enhance the performance and longevity of your engine. It may be worth sticking to a mineral oil if you’re running an older, more worn or vintage engine, but if you have a modern car, there’s not much reason not to keep it fed with a full-synthetic oil, provided it sits within your desired budget.

Johnson Alex

Alex, a seasoned automotive journalist, uses his blog to share his in-depth knowledge about the latest car models. His detailed reviews and technical analysis are valuable resources for auto enthusiasts and potential car buyers.

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