Synthetic motor oil versus mineral oil

Wooden dashboard veneer or carbonfibre? Leather seats or Alcantara? Silk undies or Lycra?

When it comes to deciding between natural materials or synthetic alternatives, it isn’t always an obvious decision, but is it the same when it comes to choosing the motor oil for your car?

We have already explored what the various multigrade engine oil codes mean, but what is the difference between mineral oil and the more expensive synthetic options?

Put simply, a mineral oil is one that is derived mostly or exclusively from naturally occurring oil, while synthetic oil is a blend of manmade chemicals.

Manufacturers of synthetic oils claim that their products are more stable and last longer for increased service intervals and, if true, some simple maths will reveal if the additional cost is outweighed by the longer intervals.

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But synthetics are also supposed to provide improved protection for your engine, particularly in the case of high-performance cars and modern cars.

The advantages of synthetic oil are due to a specific formulation for use as a motor lubricant, whereas mineral oil has been refined to the best fit from something that was drilled out of the ground. Subsequently, the tailor-made option is generally a better option, for the same reasons the best tennis racquets are made from manmade composites instead of wood.

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Highly-stressed engines including modern high-performance and race engines simply must be fed synthetic oil as stipulated in the owner’s manual or expect seriously undesirable results, but for vehicles that don’t have specific dietary requirements, there is a little more room to move.

We recommend synthetic oil for all turbocharged engines, particularly early models which do not have the efficient turbo cooling and lubrication systems of the latest vehicles. Synthetic oil’s high-temperature resistance and stability is a particular benefit for turbos where heat concentration and dissipation are more of a concern.

But what about everything else?

There is evidence to suggest all engines can benefit from the reduced wear and increased fuel efficiency enabled by lower oil viscosity, without compromising on lubricating quality, but the advantages decrease exponentially the older the engine technology gets.

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In fact, you may not be able to find a synthetic oil available with the higher viscosity that older, relatively low-tech engines require.

There is one further option. Semi-synthetic oil provides a majority of the stability of synthetic oil but at a lower cost thanks to a blend of mineral oil.

Have you ever felt cheated when you discovered that a tin of tuna in ‘olive oil’ was actually mostly soy bean? Well semi-synthetic is not like that and is blended using a maximum of 30 per cent mineral oil. It might just be the Goldilocks middle ground that suits your car and wallet.