Do I need to use a lighter viscosity oil in my car during the cold winter months?
As an AMSOIL Dealer, I get this a lot, especially in as the days get colder. The short answer is
Yes – if your manufacturer allows it.
Check in your glove box and see if what your owners manual says. In the back is usually where you find the oil recommendations.
For most vehicles, it will be 5W-20 or 5W-30. Typically, it doesn’t matter if it is -30ºF or 120ºF, modern engings are designed to be most fuel efficient using that viscosity of motor oil.
Some cars and heavy-duty equipment recommend a different viscosity depending on the outside air temperature. You might see a chart in your owners manual like this one below that shows different oil viscosity recommendations based on how hot or cold it is. Usually a lighter viscosity oil is to be used as it gets colder, during the winter.
If that is the case, use the lightest recommended viscosity during the cold winter months.
- To ensure your car gets maximum wear protection during startup
- To make sure you have easier cold weather start-ups
If you need a refresher about what viscosity is, ==> Check out this post for a detailed explanation of viscosity
In a nut shell, viscosity refers to a motor oil;s resistance to flow, and it is usually considered its most important attribute. The lower the viscosity, the easier it flows in colder temperatures. On the opposite side, the higher the viscosity of a motor oil the slower it will flow when it is cold. So an 0W-20 oil will flow easier when it is cold, compared to an oil with a viscosity 10W-30.
Explain Oil Number Meaning
What do oil numbers mean? The oil viscosity numbers are simple.
The first number, followed by a W describes the characteristics of the oil when it is cold. In this case, cold is 104ºF. The second number, describes that oils characteristics once that engine heats up, which is 212ºF.
Most of the engine wear happens when you start your engine. Why? Because a lot of the oil is drawn into the sump of your vehicle as it sits still. When you start your engine up in the morning, even if it isn’t’ that cold, a few seconds pass until the oil gets through your oil pump and finds it way to the components of your engine. THAT IS WHEN YOUR ENGINE WEAR TAKES PLACE.
That is why it is a big benefit to your engine to use an oil that flows easily during startup. Oil that flows easily will get to your engine faster, and more efficiently.
Lower viscosity oil, will get there faster, and allow better cold weather startup, when compared to higher viscosity motor oils.
Crank it up
Another benefit of low viscosity oil is that they provide less crankshaft resistance when your engine turns over. This is especially important as the weather gets below zero. The oil gets so thick that it can prevent the crankshaft from rolling over fast enough to get your engine to start.
If you are using conventional oil, they my contain waxes, which will further thicken when it is cold. Full synthetic AMSOIL motor oil does not contain these thick waxes, which is why it is the best oil for cold weather.
Check out the video for proof.
Another benefit that you will see from lower viscosity oil is better fuel economy. You may have noticed that more automakers are recommending a lighter viscosity oil in newer vehicles.
Do Higher Viscosity Oils Have Any Benefits?
With all this talk of lower viscosity oil, you may be wondering if there are any benefits to higher viscosity oils.
Oils with higher viscosity tend to give your better protection against wear. They give your engine a thicker film on your engines parts. They also tend to be more resistant to oil consumption compared to lighter viscosity motor oil.
Bottom Line: If you live in a part of the world that gets cold in the winter, you should switch to the lightest viscosity oil that your manufacturer recommends. You will maximize your engines wear protection during cold weather startups.