There are so many different types of oil available for cars, SUVs and heavy-duty vehicles that it can get confusing choosing the right stuff. Sure, in your car’s owner’s manual it does recommend what oil to use but that could be for when your car was new and not 16 years old. Let’s break down oil into its different options, namely mineral, semi-synthetic, fully synthetic and high mileage oil.
Mineral oil- As its name suggests, mineral oil consists of oil that’s been extracted from the earth and refined with additives, to be used in your vehicle’s engine. Mineral oil is a popular choice because it is relatively cheap and is what older vehicles have been running on for years. The problem is that this oil tends to break down (oxidise) sooner and struggles to handle high temperatures as a result. It is also know to be quite thick and contain certain impurities.
Semi synthetic oil- These oils are also popular because they are affordable, as the name suggests; they combine mineral oil as well as synthesised oil and can tolerate changing temperatures better. This generally means they're less volatile, so they evaporate far less, which reduces oil loss (and improves fuel economy). They're popular with drivers of bakkies and SUVs who want the high-load protection. They're a lot less expensive than full synthetics, maybe just pennies more than a premium, conventional oil.
Fully synthetic oil- This oil is totally man-made and therefore formulated to provide the optimal protection and performance for your engine. It certainly costs more; however, many modern engines, especially now with turbocharging, require an oil that can withstand head. If these oils pass stringent special tests (indicated by their labelling), it means they have superior, longer-lasting performance in all the critical areas, from viscosity index to protection against deposits. They flow better at low temperatures and maintain peak lubricating function at high temperatures. So why shouldn't everyone use them? Well, they’re expensive and not every engine needs them. In fact, there may be some features that your car's engine needs that the synthetics don't have. Again, follow your owner's manual or consult a mechanic.
Higher-mileage oil- Not all of us can afford new cars; some of us keep our cars for a long time and others love the idea of owning a classic. If you own or want to own a high mileage car, you have another oil choice, those formulated for higher-mileage vehicles. There are many cars on the road which have more than 150 000km on the clock. So the oil makers have identified this as an area of customer interest, and have specially designed oils they're recommending for these vehicles.
Why does my older car require special treatment?
When your car is somewhat older and has considerably more mileage, you may notice a few oil stains on the garage floor. It's about this time that you need to add a quart more often than when the vehicle was new. Crankshaft seals may have hardened and lost their flexibility, so they leak (particularly at low temperatures) and may crack. The higher-mileage oils are formulated with seal conditioners that flow into the pores of the seals to restore their shape and increase their flexibility, which reduces the risk of a leak. You may also have noticed some loss in performance and engine smoothness as a result of engine wear on your higher-mileage vehicle. These higher-mileage oils also have somewhat higher viscosities and may have more viscosity-index improvers in them. The result is that they seal the piston-to-cylinder clearances better, and won't squeeze out as readily from the larger engine bearing clearances. They may also have a higher dose of anti-wear additives to try to slow the wear process.
In our next oily bits article we’ll cover exactly what those numbers on your oil bottle mean and also run through the various additives that manufacturers use in their oil to help protect your engine.