Engine Oil Buying Guide
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It's very easy to get confused by the sheer quantities of different types of engine oils that are out there for use in cars today. There's "5W-30" this, "SJ rating" that, and the whole "mineral versus synthetic" debate; but what does it all mean? A good rule of thumb would be that the right oil for your car's engine is usually one that at least meets and/or exceeds the standards of the requirements listed by your vehicle manufacturer (as found in the owner's manual/handbook, or workshop manual at a pinch).
If your car needs a particular type of fully-synthetic oil of a certain grade, the use of a mineral or semi-synthetic engine oil that doesn't have the right qualities or capabilities can potentially lead to disaster. Conversely, over-capitalising on a high-quality fully-synthetic oil on a car which doesn't need - or won't benefit - from such an oil isn't ideal either.
Where you might want to consider alternative engine oil choices would depend on many factors. For example, power-enhancing modifications to your engine might dictate the need for extra lubrication or protection, whilst how new or old the engine is - and thus perhaps necessitating added zinc to minimise metal-to-metal contact or extra detergent additives for cleaner running etc. - is also a factor. The type of driving you do also has a role to play; a vehicle used for daily short-trips might benefit from additional anti-wear properties via the inclusion of molybdenum disulfide additives, whilst the occasional track day or motorsport event would dictate yet another type of oil with perhaps an assortment of friction modifiers and compounds to maintain performance under higher sustained temperatures.
The technical makeup of exactly what goes into different types of engine oils is a complicated process and the precise "recipe" of base compounds and additives is adjusted in order for each oil to meet both a specific purpose and performance level, and to satisfy different ratings and standards by bodies such as the Society of Automotive Engineers (SAE) and the American Petroleum Institute (API). While engine oils are generally made from a combination of petroleum hydrocarbon base stock and an assortment of additives and compounds, instead of the distillation of crude oil method used to produce mineral-type oils, synthetic-type oils are made up of chemically-made crude oil or by-product compounds and, depending on their "API Group" classification and other inclusions, a polymerisation of an Alpha-Olefin or the use of wholly synthetic compounds known as Esters. As the name implies, oils known as "semi-synthetic" are a combination of conventional mineral engine oil and synthetic engine oil within certain ratios.
Which type of engine oil is exactly right for your car - mineral, semi-synthetic or fully-synthetic - is largely down to both what the original manufacturer (or your mechanic) recommends and your budget. Generally speaking, fully-synthetic oils tend to be higher-performing under particular circumstances than their less-expensive alternatives but it depends on many, many factors. In certain instances, a quality mineral or semi-synthetic oil can potentially perform just as well as a similar-grade fully-synthetic version in service, as long as they're compatible with the engine's requirements. It's one of those "it depends" type of scenarios so consult an expert for specific advice!
"What about those 0W-30 or 10W-40 codes I see on oil containers?", I hear you ask? Well, that is all about the oil's viscosity, namely it's resistance to flow and shear (i.e. film strength) and, the greater the number, the higher the viscosity. The vast majority of engine oils sold in Australia are multi-grade oils where the first number indicates the oil's viscosity at the operating temperature the engine would experience when near-cold - sometimes referred to as the "Winter" rating hence the "W" designation - whilst the second number indicates the oil's viscosity measured at 100 degrees Celsius, close to the typical operating temperature in a normally-running engine.
If extra engine protection during cold starts is desired then a multi-grade oil with a low first number is normally the preferred option whilst the more important grade of viscosity at operating temperature, indicated by the second number, should be matched to your specific engine's requirements. It's worth noting that the actual measurement of viscosity and how the oil matches up to the SAE oil viscosity ratings occasionally varies slightly between oil manufacturers and, for those hell-bent on picking the right engine oil, it is sometimes worth researching the specific Kinematic Viscosity (measured in centistokes, cSt) at the different temperature extremes of engine oils under consideration and matching those to your engine's requirements.
Ultimately, when it comes down to it, if you buy the best oil that is right for your car that you can and change it regularly then you can't go too far wrong. I've never seen an engine suffer any harm from having the right oil that is too-new... unless someone forgets to put the sump plug back on, doesn't notice the pool of fresh oil on the floor and starts the engine, that is...!
Here at Automotive Superstore we are well-equipped to supply all of your engine oil needs - click here to explore our range!