Car oils: Should I change them in winter?

The cold not only tests the endurance of people, but also of machines. But do we need to change the oil in our engine because of the cold?

Although this year it was a little late, the cold arrived in our country and in fact... heavily armed. The temperatures dropped sharply and if we understand it easily in Athens, then the inhabitants of the countryside and mountainous areas experience it even more strongly. But what about our cars? Do they like the cold, do they find it indifferent or does it burden them? Let's put things in order...

The older ones used to change the oil in their cars during the winter season. They had this habit even more strongly in areas where the thermometer shows well below 0 degrees Celsius in winter, while there are not a few who still do it.

Did they do well? Based on oil technology then, yes. But today things are different. Car oils have evolved and especially full synthetics, but also semi-synthetics, come to solve our problems.

In general, the tendency of oil is to become thick when cold and thin as it warms. If we leave it at room temperature we will see that it has a dense but fast flow, while as we freeze it we will notice that its resistance to the flow increases.

We will see exactly opposite phenomena if we heat it. It will become highly liquefied and flow faster, like water. Thanks to special additives, modern oils have the ability to change their properties depending on their temperature.

Have you ever wondered what those… strange things written on the packaging are? SAE 5W 30, for example?

Originally, SAE stands for Society of Automobile Engineers. They created a scale, called viscosity, which is defined by the oil's resistance to flow. The lower the number, the "thinner" the oil, so it doesn't get as "thick" in the cold. In 5W 30, it means that the oil has a viscosity of 30 in normal engine conditions (at operating temperature), but when the engine is off and we have winter, the viscosity from 30, goes down to 5, for a better flow of the oil inside the engine by the start, until it reaches temperature.

The “W” stands for Winter, so 5W 30 oil tells us that it is SAE 5 when cold to stay thin and SAE 30 when operating temperature (80-120 degrees Celsius) is reached to adequately lubricate the engine.

To break it down even further, if the oil was left with SAE 30 when starting an engine in very cold temperatures, it would be quite difficult for the engine to start and the pressure on the oil filter, starter, engine and even the battery would be large, due to the resistance of the thick oil.

Conversely, if the oil was left with SAE 5 at normal engine operating temperature, then it would become incredibly thin, like… water, so it would not provide effective lubrication of the moving parts. So synthetic oils have this property, to change their characteristics. However, keep in mind that the greater the SAE deviation of the oils, the more their service life is reduced. SAE 5W 40, 5W 50, 10W 60, etc., need to be changed more often, due to -and- the large fluidity deviation they show when they are cold or when they are at operating temperature. But here we go to more specialized options and not the most common ones (5W30, 10W 40) so it does not concern the majority of vehicles.

Should I finally change it?

No! The manufacturer has also provided for winter, thanks to the variable viscosity depending on the temperature of the oil. There is no reason to change our oil in the winter to make the engine run better and we use the exact same type that we put in in the summer. Especially in Greece, where the cold lasts only a short time and we do not face conditions... of polar cold in the majority of the country, such a move would be unnecessary.