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Driving Concerns

Filtering the truth on synthetic oil Add to ...

Are there specific filters to use when using synthetic oil? Even though synthetic oils can last longer between oil changes, my Nissan dealer says the oil filter is a regular filter designed for conventional oils. That means one must change synthetic oils at the same intervals as if one was using mineral oils. Is this correct? – Peter

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Car makers want you to follow their oil change schedules, even if you upgrade to synthetic oil – but to blame that on the filter is straining the truth, our expert says.

“Filters are filters, it doesn’t matter what kind of oil you’re using,” says Dennis Mott, automotive professor at Centennial College in Toronto.

Filters are the kidneys of your engine, and they’re not fussy – they’ll screen debris out of any engine oil, whether that oil is conventional or synthetic, Mott says.

So, synthetic oil doesn’t require a special type of filter – but here’s where the words get murky. Yes, you can buy synthetic oil filters, but they’re not meant solely for synthetic oil – they’re called synthetic because they’re made of more synthetic fibres than normal paper filters.

Putting filters aside for a second, upgrading to synthetic oil doesn’t necessarily mean you can go much longer between oil changes, Mott says.

“Synthetic oil, its benefit is not that you can go longer between oil changes,” Mott says. “It’s good because it maintains its viscosity in extreme cold or extreme heat.”

Engine oil doesn’t only lubricate – it cleans your engine and it carries heat away with convection, Mott says.

“So you want an oil that doesn’t get thin under heat, or get thick during a cold start up,” he says.

Nissan says you can upgrade to synthetic oil if your engine takes conventional – but it doesn’t recommend extending oil change intervals just because you’re using synthetic oil. It says you should follow the schedule, period.

“Some of our vehicles are designed to take advantage of the properties offered by synthetic oils,” Marsaud says. “On other vehicles, the use of synthetic oil will not hurt your engine, but it is unlikely to increase performance or extend the life of the engine if the proper maintenance is done.”

Nissan recommends Nissan oil filters, regardless of the type of oil you’re using.

“While we can’t comment on other manufacturer’s filter designs, Nissan filters are designed to properly filter the microscopic particles from engine oil whether it is synthetic or traditional motor oil,” says Didier Marsaud, Nissan Canada’s senior manager of corporate communications, in an e-mail.

What matters when replacing a filter? How well the filter does its job – get one with a filtration rate that’s the same, or better, than the filter your car came with, Mott says.

“You want 20-40 microns or smaller,” Mott says.

Certain filters (all of Nissan’s, the company says) have added features – like an anti-drainback valve that holds the oil in the filter after the engine has been shut down.

“It allows oil to more quickly reach the top of the engine on startup.” Marsaud says. “Not all filters are alike.”

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

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