Choosing the best oil for your car

If you’ve ever stood before shelves of engine oils and felt overwhelmingly confused about which one to buy, you’re not alone. Although they all do a similar job, which is to lubricate and help cool all the moving internal parts of an engine, there are some good reasons why you should choose the correct engine oil for your vehicle. 

Each type of oil serves a different car make and varying temperatures, conditions, and climates. Picking the correct one will help your car perform optimally. 

The good news is that New Zealand temperatures aren’t extreme and don’t vary wildly across the country. This means that oil grade requirements for individual vehicles remain consistent throughout each season and across the entire country.

Here is a breakdown the different oil grades to help you understand the various types available and choose the best one for your car. 

Engine oil viscosity

Viscosity ratings tell us how thick the oil is at a given temperature. Many car manufacturers recommend multigrade oils, which are thinner at cooler temperatures to allow for faster circulation, and thicker in high temperatures to protect the engine.

A common multi-grade oil viscosity rating is 10W-40. The first part – 10W – describes the viscosity of the oil at low temperatures and the ‘W’ stands for ‘winter’. The lower the number, the thinner the oil, and the better the oil’s cold temperature performance. The number after the W describes how thick the oil is at the engine’s normal operating temperature.

Your vehicle’s manual will specify the ideal oil viscosity, so it’s best to stick to that, or something pretty close, unless you need to alter it for use in extreme temperatures.

Types of oil

There are three main types of oil available: mineral, synthetic, and semi-synthetic. All oils are made from crude that come from the ground. The difference is in the oil refining process and the additives added to it.

Synthetic oils are made from an advanced refining process that removes more impurities from the oil and allows individual molecules in the oil to be tailored to the demands of the modern car engine. This is a purer oil and is generally of higher quality, so it offers a higher level of protection due to increased anti-friction properties. The bottom line is that it supports less engine wear, increases fuel economy, and means a longer engine life.

Mineral oils tend to be used for older vehicles and in vehicles with higher mileage, or if the engine is a bit tired and burns too much oil. There’s no need to spend on more expensive oils if the engine burns through it consistently. 

Semi-synthetic or part synthetic oils are a blend of both mineral and synthetic oils. They provide better performance, protection, and fuel economy than mineral oils, but are not as good as a full synthetic. This is a good in-between oil for well-kept, low mileage cars that don’t need full synthetic engine oil.

Your car’s manual should specify which type of oil you should be using. If you’re still unsure, have a chat with your mechanic or your local auto spares expert and they can advise the best type for your vehicle.