Viscosity and ambient temperature
In everyday operations, it is preferable to maintain a viscosity that is as consistent as possible to ensure optimum lubrication over the entire temperature range. Engine oils with low viscosity margins facilitate trouble-free, year-round engine operation under all kinds of operating conditions: from cold starts in winter to working in regions with the hottest temperatures in summer.
SAE is the acronym for the Society of Automotive Engineers. This is an organisation that has defined a set of classifications for oils.
For many buyers, the SAE classification (for example, 10W-40) is the decisive quality criterion when choosing the right engine oil. It must be remembered, however, that SAE viscosity classes do not represent performance demands with respect to the engine or gearbox, but merely specify the viscosity at standard reference temperatures.
Please also compare the stipulations of the individual engine manufacturers laid out in the instruction manual for your machine.