Frigid weather can be a torture test for motor oil. Cold temperatures can lead certain grades of oil to become thick and gloopy, hampering your engine’s performance--or its ability to turn over.

“Traditional oil can almost become solid in a vehicle exposed to extreme cold temperatures,” said George Zhang, a chemist for Valvoline. “In the worst cases, hardened oil can even prevent the car from starting.”

Do you live somewhere especially frosty or plan to travel in frigid climes? Consider investing in oil formulated for cold weather.

Colder climates can hamper the performance of conventional oils, while synthetic grades typically handle the cold better.

The choice isn’t just between traditional and synthetic motor oil. There are even engine lubricants that are blends of synthetic and conventional motor oils.

Synthetic oil has become far more reliable and efficient since it first became available several decades ago.

“In the past–15 to 20 years ago–a lot of the materials in synthetic oils made rubber seals get brittle,” Zhang said. “But this problem has been corrected. The oil has gotten highly refined and doesn’t make the seals brittle anymore.”

But what do those numbers and letters mean?

Oil codes can help you choose the right fluid for your vehicle. The “W” stands for winter; the number preceding the “W” refers to a cold weather viscosity, or thickness, at a certain temperature. A 5W- motor oil flows better at colder temperatures than 15W- oils in the same conditions.

The numbers after the “W” refers to the oil’s viscosity at hot temperatures. The higher the number, the thicker the oil at a specified temperature.

Check the vehicle owner’s manual for specific recommendations for your driving conditions. Or ask your service advisor for help choosing the right product.

Below, oil manufacturers offer some tips on oil maintenance and benefits of a winter-formulated oil.

• Check your owner’s manual for the proper type of oil. It will say the recommended grade and offer advice on how frequently to have it changed.
• Choose an oil that’s designed for your engine. Some oils are specially formulated for high-performance engines, while others are best for engines that experience a lot of city driving.
• Older vehicles might benefit from using high-mileage oil. Oil designed for a high-mileage engine has more viscosity, thickness, than conventional. The thicker fluid compensates for wear and tear on the engine. For example, older vehicles have more space between bearings.
• Routine maintenance. Regular oil changes can help wring every last mile out of your engine. It’s an inexpensive way to keep your vehicle running in top performance.
• Synthetic oil comes from conventional oil. The base of synthetic oil is crude oil, which is distilled and refined before specifically engineered chemical compounds are added.
• Synthetic oil evaporates slower than conventional oil, and offers resistance to thermal breakdown, the formation of engine sludge and oxidation--when oxygen contaminates the oil, which can degrade its quality and even cause it to go rancid.