5W40 and it's for diezel and it's a synthetic ??? I think it will work in the polar circle, but it will disappear faster in our country. The oil grade depends a lot on the mileage and condition of the engine. A colleague in our climate should pour at least 15W40 as a year-round oil. This is a subsistence minimum for the engine

The first two digits indicate the viscosity grade at low temperatures and the last at high temperatures. In this case, 15 is the maximum viscosity that the oil can reach at a given negative temperature, the negative pumpability limit temperature is -20 ° C, the minimum viscosity at 100 ° C. Whereas 40 means minimum viscosity at 100 ° C, maximum viscosity at 100 ° C, minimum viscosity at 150 ° C and a shear load of 106 1 / s (HTHS).
Moderated By robokop: Warning for writing idiocy. Grade 15W40 oils are mineral oils, expert.