Winter Engine Oil

Winter engine oil hasn’t been used by car owners for a long time, so forget the term altogether. If the engine oil you pour into your engine has a viscosity grade like 5W-40, 10W-30, and so on (that is, two numbers separated by the letter W), it’s an all-season oil meant for year-round use (and this is exactly the kind of oil the vast majority of car owners run). What matters here is that only the first number, the one before the letter W, has any bearing on how the oil behaves in winter conditions. You can read more about what the viscosity index means in our article on oil viscosity.

So, if the low-temperature viscosity of the engine oil you normally use suits your region’s climate, and the starter and battery are both in good shape, feel free to keep using the same oil as before. High-temperature viscosity (the second number in the code) has no bearing whatsoever on winter driving, because the engine’s operating temperature is the same in winter as it is in summer.

If you’re not confident about the expected temperatures, or about the state of your starter or battery, you can switch to an engine oil with a lower low-temperature viscosity rating (for example, moving from 10W-40 to 5W-40). Keep three things in mind when you do:

1. Switching engine oil brands puts extra strain on the engine, so it’s well worth getting in one more oil change before the frosts set in (for more on how to properly switch to a different engine oil, see the article on changing your oil).

2. Guaranteed compatibility only applies within the same manufacturer’s oils, so if you do switch brands, try to at least stay loyal to the same maker.

3. The engine oil you choose for winter use must always correspond to the car manufacturer’s recommendations (for more on all this, see the article on how to choose the right engine oil).