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The primary purpose of the oil in your engine is lubrication, to prevent all those moving metal parts from grinding together, creating friction and heat and wearing those surfaces away. By providing a thin separating film between moving parts, it reduces friction, heat and wear.
The primary purpose of the oil in your engine is lubrication, to prevent all those moving metal parts from grinding together, creating friction and heat and wearing those surfaces away. By providing a thin separating film between moving parts, it reduces friction, heat and wear.

Rob's Garage

When should I switch my car to synthetic oil? Add to ...

Hello,

I just read your column about synthetic oil and was wondering when I should switch to synthetic? I have a recently purchased 2010 Mazda 6 GT with about 25,000 km and have always taken my other cars in for regular maintenance / oil changes. Also, once you switch to synthetic you have to stick with it, do you not?

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Thanks, Adam

To your first question: the best time to make the switch (with a new car), is after the first oil change. Synthetic oils do such a great job of lubricating that they don’t allow a new engine to “break in.” The execution of a proper engine break in focuses on fitting the new piston rings against the walls of the cylinders. You want the rings to wear out a small amount so that they can take on the shape of their respective cylinder. Synthetics are too slippery to provide enough of a wear factor, so leave the initial fill of oil in the crankcase to do this job. After the recommended change interval is reached, enough ring wear will have taken place to break in the engine, yet the engine will still be fresh enough to take full advantage of the synthetic fill.

In your case, 25,000 kilometres is still considered low which puts you in a position to still take advantage of using synthetic engine oil.

To answer your last question; once you begin the regimen of using synthetics, you can bounce back and forth between mineral or synthetic based oils all you want. It’s still just a lubricant, but once you start, you will never want to go back. Although you might not notice, the engine will run smoother and cooler.

If I could add to your questions, try running a thinner grade of oil. Synthetics do such a good job of lubricating, sealing, cooling and cleaning that you can run the lowest viscosity that is recommended by the manufacturer. This is especially advantageous if you start your engine many times a day. The thinner the oil, the quicker the oil pump can pump the oil to the top of the engine to lubricate the valve train and get the oil to the crankshaft journals to lube the crank pins and main bearings. Engine start-ups cause the majority of engine wear. Another advantage is winter starting. Thinner oil in the crankcase will be less resistive to twist over by the poor starting motor in cold temperatures.

Oh, and change the oil at the recommended intervals outlined in your owner’s manual. Synthetic or not, oil still gets dirty and needs to be replaced along with the filter. And don’t be shy if your manual recommends extended mileage or an extended time frame between changes. We are soon going to see oil change intervals of 10,000 or even 25,000 kilometres!

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

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