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Which oil is best? Whichever one the manual recommends

  • Choosing a car at dealership. Thoughtful grey hair man in formalwear leaning at the car and looking away

Q. What?s the difference between motor oil brands, grades and types?

A. Use only the grades and letter-classification of oil, or the updated equivalent, as recommended by the automaker for your vehicle.

On the bottle, look for the American Petroleum Institute ?starburst? and ?donut? logos indicating that the oil meets API standards.

Inside the API donut symbol, you?ll find the grade and service category. A Society of Automotive Engineers graded SAE 5W20 oil, for example, is a multi-grade product that acts like a 5 in winter cold, and like a 20 in warmer temperatures, or, as the engine heats up.

Lower numbers indicate thinner oil grades.

The current oil service category for gasoline vehicles is ?SN.? Such oil meets the specifications for new cars and supercedes all previous letter grades alphabetically. This means that SN oil can also be used in older cars where the automaker calls for an SM, SL, SJ rating.

For diesels, the current service category is CJ-4, which supercedes all predecessors.

You may also find an International Lubrication Standardization and Approval Committee classification on oil bottles. The current ILSAC standard is GF-5, which supercedes all previous standards of GF-1 through GF-4.

If your automaker recommends 5W20, SN, GF-5, for example, any brand of oil with those markings will satisfy your warranty requirements.

Oil brands differ in their additives, and, naturally, the costlier brands claim theirs are better, although any ?SN? oil meets minimum standards to satisfy your warranty. Between oil changes, it?s ideal to top-up with the same oil, so it has the same additive package, but this isn?t essential.

You also have a choice between regular, synthetic or semi-synthetic motor oil.

Synthetics have superior flow properties to provide vital lubrication faster in cold weather immediately after start-up, which can reduce engine wear. Synthetics also outperform conventional oil at resisting thermal breakdown at high operating temperatures.

Semi-synthetics are a blend of synthetic and regular oil, but likely far below a 50:50 ratio. Synthetic and regular oil can be mixed, so you might consider a do-it-yourself blend instead (e.g. 2L synthetic plus 2L regular oil).

Synthetic oil is the most expensive. But keep in mind the reason you change your oil at the automaker?s suggested service interval is because it gets dirty with sludge, by-products of combustion and other contaminants.

So, the claims of some oil brands to the contrary, you can?t necessarily extend your service interval when using synthetic oil, and doing so may void your new-car warranty.

Many vehicles now have an oil sensor that tells you when to change your oil based on how dirty it is rather than from a pre-determined automaker?s guideline, such as three months or 5,000 km.

If you are changing your own oil, please dispose of waste oil properly. Contact your local municipality for information. A local auto garage might also accept it for recycling. Illegally dumping used oil can result in fines and a hefty bill for clean up.

Email your non-mechanical questions to Eric Lai at [email protected] Due to the volume of mail, personal replies cannot be provided.

  • Which oil is best? Whichever one the manual recommends April 20, 2011 -- Centennial College -- "Volvo-Mack Modified Apprenticeship" students Christopher Madhav makes an oil change on a class 8 Volvo truck at Centennial College, on Wednesday April 20, 2011.__(Adrien Veczan for the Toronto Star)
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