What is the viscosity of a lubricant?
Viscosity is the resistance of a liquid to flow and, in the case of lubricants, it is an essential characteristic to take into account when choosing which is the best product for you.
Vehicle manufacturers are responsible for establishing the most adequate viscosity for their different models, which is included in their manuals. Usually, several viscosities are recommended since it may be necessary to adapt the viscosity to the vehicle's usage conditions and the weather conditions.
Viscosity is not indicative of the quality or suitability of the oil, it is just one of the properties to take into account when choosing a lubricant. However, quality level is what sets one lubricant's properties apart from another. These quality levels are usually indicated on the label.
It is not advisable to mix lubricants with different viscosity levels. You should only do this when really necessary such as refilling when the oil level is low. You should use an oil with the same quality level as the one used in the vehicle and, if possible, from the same manufacturer.