The article was written in collaboration with experts from engineswork.com – a site made by auto experts with many years of experience in this niche.
We will repeat for the umpteenth time – in no case should you fill the engine with oil, the viscosity of which is not provided by the car manufacturer specifically for your engine! The car manufacturer took into account all possible driving modes on your engine and recommended exactly those viscosity parameters that are optimal for THIS motor.
5W-20 is a less viscous oil, that creates less friction during operation, relieves parts, due to which it is more economical – it reduces fuel consumption, albeit insignificantly. It is easier to pump such oil to the oil pump, but if it does not fit your car according to tolerances, oil starvation may occur, the viscosity of the oil film will not be enough.
Both options are suitable for use in winter, the cold start will be the same, but as soon as the temperature rises to 90-100 degrees, there will be a problem with high-temperature viscosity. That is, the low-temperature indicators for oils are approximately the same, and the high-temperature ones are different.
In general, the difference between the oils is not very big, they both have high fluidity. But it is imperative to choose according to the recommendation of the engine manufacturer, and not according to your own preferences. The low viscosity of 5W-20 can harm the engine if it is not recommended by the manufacturer, the oil film is very thin and can break in urban driving. 5w-20 is most often used in modern engines of Japanese cars, all CPG clearances and oil channels are designed for this viscosity.
By the way, the smaller the difference between the first digit before W and the second after, the higher the replacement interval. Therefore, all manufacturers are trying to switch to such viscosities in order to save fuel, the longer the replacement interval – less mining, less harm to the environment.
5W-20 or 5W-30 – which is better
In this matter, there is no such thing – better or worse, depends on many factors: the brand of the oil, the existing tolerances, etc. You also need to choose based on the recommendations of the engine manufacturer, if the use of 5W-20 is allowed, and it is suitable for the climate of the region where the car is operated, then you can fill it in for the sake of saving fuel. But it is worth remembering that this oil is not for hot climates.
If the car “eats up” the oil, then it is better to use 5W-30, again, if there is a recommendation for such a viscosity from the engine manufacturer, but at the same time understand that increasing the viscosity of the oil used will solve the problem only for a while, you need to check the engine and find the reason for the increased consumption.
With regard to use in winter, both of these oils are “winter”, that is, they can be used in any season, but are suitable for low and very low temperatures. When choosing, you need to be guided not only by the specified SAE but also by the technical characteristics. For example, the oils indicated just above have the following pour point: SHELL Helix Ultra 5W-20 -36 degrees, 5W-30 -52, although there should not be a difference between them, it is significant.
Also, when choosing, we pay attention to the dynamic viscosity of the CCS cold-cranking simulation – the lower the indicator, the easier it is for the starter to crank the cold engine. If the characteristic is at the uppermost limit, which for 5W is 6500, there will be no margin, starting the engine at -30 will be quite risky, and further upward – the lower the indicator from the redistribution, the greater this margin will be, the engine will start quickly and safely.
Can I blend 5W-20 and 5W-30?
In theory, yes, but it should be borne in mind that the viscosity will become average between these values, that is, 5W-25, depending on the proportions. If you have already decided on mixing, it is better to use the products of one manufacturer, and not to abuse such things at all, but to use the same oil both for topping up and replacing.
