Autowirez Blog

Here we discuss in detail the differences in Synthetic and Mineral oils and how well they perform for your engine.

In addition to lubrication, motor oil cools your engine too. Both synthetic and mineral engine oil contains additives which help increase the performance and lifetime of the oil. The differences between these types of oils are all in the molecular makeup. Synthetic oil has a very consistent molecule size which gives the oil very good and consistent properties. Mineral oil being a product of nature has lots of different sized molecules in its makeup. The advantage of synthetic oil is that it has a more stable suite of properties in that the molecules are all of very similar shape and size. This allows synthetic oil to operate effectively in both high and low temperatures. Mineral oil normally evaporates at around 350ºF and synthetic 600ºF, so the heat tolerance of synthetic motor oil is much better.

Mineral oil is produced by refinery distillation of crude oil, coupled with extraction processes to filter out undesirable components. This process generally gives satisfactory results but does not have the ideal molecular composition for modern, high performance engines. Synthetic oils also derive from crude oil, but by carefully selecting the feedstock and using a hydrogen-based synthesis process, we can physically restructure the hydrocarbon molecules to create a more consistent product. This gives the synthetic oil improved performance characteristics over conventional mineral oils.

What do the SAE numbers mean?
The SAE Society of Automotive Engineers numbers relate to the weight or viscosity of the motor oil. Oils which have a single number such as SAE 30 are single grade oils which get thinner as the oil heats. Where two numbers are shown, normally arranged with a W as (ie. 15W 40) the oil is multigrade. Multigrade motor oil generally offers better lubrication throughout the engine’s operating temperature range. The lower the W (ie. 5w 40) number, the thinner the oil will be at low temperatures. This means that on cold winter mornings, on starting your engine, oil will flow almost instantly throughout the engine reducing wear and increasing engine life unlike mineral oils. The other number (ie. 5W 40) relates to the oils performance at normal engine operating temperatures which test engineers set at 100ºC. Unlike the W number, the higher this number is the better high temperature performance.

Multigrade oil was introduced in the 1950’s to eliminate the need for seasonal oil changes in summer and winter to accomodate hot and cold weather. In effect, multigrade oils could be run all the year round as there was no need to change the oil viscosity to suit the season.

Advantages of synthetic over mineral oil
Many petrol and diesel cars now have higher performance engines with multiple valves, electronic fuel injection, turbo and super-chargers all as standard. They run faster, tighter and consequently hotter but develop more power than ever before. As a result, lubricant is now under greater stress and oil quality is of greater concern. Both synthetic and semi-synthetic motor oils are formulated to withstand the added stress and longer oil change intervals demanded by cars today.

Summary
If you are looking for a new motor oil for your vehicle, look for the one with the biggest difference between the two numbers. In cold climates, look for an oil that has a low W number to protect your engine on the cold mornings. For example, 5W 50 is going to be better for your engine that 15W 40. Although the price of the oil usually reflects these ratings, knowing what these numbers mean could help you can pick up a bargain.

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