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Shouldn't synthetic car oil last longer than conventional?

When I had a 2009 Camry, the recommended oil change was every 8,000 kilometres with conventional oil. Now I have a 2012 Camry and the recommended oil change is still every 8,000 kilometres, but this time with synthetic oil. I thought, if we used synthetic, oil changes would be less frequent? – Guy

I don't think synthetics should be called oils because they are a chemical composition, compared to "oil," which is derived from that black greasy stuff sucked out of the earth.

It is widely believed that synthetic lubricants will outlast petroleum-based oil by a factor of two or three. However, it is important to note that synthetics were not developed with added life in mind, rather the ability to withstand greater extremes in temperature. This is especially important in passenger vehicles in this country because cold starts are the hardest moments in an engine's life – the few seconds before a protective layer of oil or lubricant is placed between moving parts.

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Oils tend to drain away from these places over time while lubricants stick around longer. Synthetics are also quicker to get to the job site during a cold start. Here we have a primary reason for some manufacturers to recommend synthetics – greater protection during cold starts and thus longer life.

Another major factor in choosing synthetics over oil is that they help improve fuel mileage and reduce emissions – two major factors in any modern motor vehicle, especially to the manufacturer, who has to meet tough regulations regarding both mileage and emission.

So far, we have three advantages for synthetics and no mention of longevity or extended change intervals.

Another factor is that most drivers, without knowing it, operate their vehicles under what the oil industry calls "extreme" or "severe" conditions." This does not mean driving really fast or towing huge loads; it can mean not driving far enough or long enough to allow the engine and its fluids to get up to and remain at operating temperature long enough to allow contaminants to be boiled off or evaporate.

Most manuals spell out oil change intervals for normal and severe use.

Send your automotive maintenance and repair questions to globedrive@globeandmail.com

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