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Winter Oil Viscosity: 3 Things You Need to Know

You probably don’t think much about oil viscosity, and most of the time there’s no need to — unless you happen to live in an area that regularly deals with harsh, cold winter weather. That’s when viscosity, which is the measure of how well a lubricant flows at a given temperature, starts to take on an important role in keeping your engine protected.

Check out these three things you need to know about winter engine oil and how viscosity can affect your vehicle’s performance and longevity.

1. Understand Viscosity Numbers

The oil viscosity numbers on the bottle refer to how quickly the oil will flow, representing its grade. Most modern automobiles use multigrade oils. This means they flow at one rate at 0 degrees Fahrenheit and another when heated up to 212 degrees Fahrenheit, which is the Society of Automotive Engineers’ (SAE) standard operating temperature in an engine. The lower the number, the thinner an oil acts, allowing it to flow more easily.

Multigrade oils separate the two numbers with a “w,” so when you see a rating of “5w30,” you’re looking at a lubricant that flows like a 5-weight oil when cold and a 30-weight oil when warm. This means at cold start-up, the oil stays thin enough to burst rapidly through the motor and protect it during those crucial moments after you turn the key, then thickens its flow for more effective protection against heat once the engine has warmed up.

2. Pick the Right Weight

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If you live in a cold climate, a multigrade oil is a must, as a straight weight or single-grade oil simply won’t be able to adequately protect your motor as it moves from one temperature extreme to the other.

Your vehicle’s manufacturer almost always publishes a range of safe oil weights in the owner’s manual, often with a set of temperature guidelines for each. Stick with these and you’ll be safe — but if you happen to live in an area where wind chill can drop overnight temperatures dramatically, you may want to consult your mechanic about moving to a thinner multigrade oil.

3. Go Synthetic

Oil viscosity isn’t the only predictor of how well an oil will flow when it’s very cold outside. Synthetic oils are much better at resisting the thickening effects of winter weather than traditional, non-synthetic lubricants, without sacrificing their ability to coat internal engine parts. As a result, synthetic oils not only protect better when you first fire up the ignition, but they can also make start-up easier by reducing the initial resistance in the motor as the starter turns the mechanical components. In a situation where your battery is also fighting against a deep freeze, this oil viscosity boost can mean the difference between driving home and being stranded.

Choose the right oil to gain peace of mind during the winter months — both when you start your vehicle, and in terms of overall engine protection in the cold.

Check out all the chemical products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on oil viscosity, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Flickr.

about author

Benjamin Hunting

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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