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Your article on oil changes and following manufacturer guidelines was valid, but I thought I thought you might find it interesting to know that guidelines for the identical cars can be different between Canada and the United States (for unknown reasons).

In 2008, I purchased a new Toyota Sienna AWD in the United States and legally imported it into Canada. I was taking it to a Toyota dealer in Toronto for minor warranty service and they told me that, at 5,500 kilometres, I was overdue for an oil change. I was given a lecture about how if I didn't follow their guideline, it would void my warranty.

I told them I was following their guideline and pulled out my U.S. manual which recommended 5,000 miles (8,000 km). When I challenged them on this, they had no explanation as to why Canada would require more frequent oil changes. The vehicles are identical and made in the same Ohio plant. When it was imported, the only modification required for Canada was switching the odometer from miles to kilometres. I was told that engine, emissions, etc., were the same as the vehicles sold in Canada.

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At a 5,000-km service interval they have the potential to get 60 per cent more oil changes from the owner. I told them I would continue to follow their guidelines and I expected my international warranty to be honoured and I was happy to hear they confirmed they would. It might be interesting to know if this was an anomaly or if other cars and other manufacturers are following this practice, and if so, why? – Gary

Without getting into the practices of many different manufacturers, I would suggest the difference is climate.

Manufacturers conduct extensive testing to determine the best service intervals for individual markets. Just as fuels differ from one to another, so do atmospheric conditions. Generally speaking, Canadian weather is more severe, especially on the colder end of the scale. Cold starts are the most stressful time for an engine, the oil is thick and protection at its lowest.

The more frequent change intervals here tell me this manufacturer is being cautious with respect to engine wear and warranty claims. Granted, there are areas south of the border where winter can be a nasty, but if you take the continental United States as a whole, the average winter is far warmer there. Keep that average in mind – the service recommendations have to take into account there are far more vehicles sold in warm areas of the United States than in the northern states. For example, there are more new vehicles sold in two states (California and Texas) annually than in all of Canada.

***** Foamy Oil *****

Last November, I obtained a 2004 Mazda RX-8. I notice that the book asks for a 5/20 oil, which is thin and, after having an RX-7 for the last 20 years and using 10/30, was surprised by that. Now, when I tried to check the oil level, I realize that it was almost impossible to see it properly. It seems to be a bit foamy and difficult to see. I do have a level gauge in the console, which shows a bit more than half, but I would like to know if this is normal for thin oils or if I have too much oil in, resulting in a foamy oil. To clarify, the car is running fine. – Jose

One of the distinct features of the rotary engine is that it "uses" or requires more oil.

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Mazda has a great deal of experience with this engine and has altered its recommendations over the years. The thinner oil is per its recommendations and the fact you can hardly see it, indicates it is clean – and that is a good thing.

The foam may be an issue, however. If there is water mixed in with the oil, that is bad; the source should be located and cured. If there is air in the oil, that may come as the lubricant passes through hundreds of tiny orifices on its trip through the engine picking up a bit of air at each passage. Under normal operating conditions and temperature, any water or air quickly evaporates or disappears.

Make sure to check your oil after the engine has been run for a while to allow this opportunity. Cold weather or short trips that do not allow the engine – and oil – to get up to proper temperature can be the problem.

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