Whats the difference between multigrade and monograde engine oils?
Multi-grade engine oils have a viscosity grade designation in the format ‘SAE xxW-yy’ (eg 15W-40) compared to mono-grade viscosities which are in the format ‘SAE zz’ (eg SAE 40). These viscosity grades describe the fluidity of the oil under various temperatures. The monograde viscosity designation describes the fluidity of the oil at 100 degrees Centigrade – with higher numbers corresponding to thicker oils. Common viscosity grades for monograde engine oils are SAE 30, SAE 40 and SAE 50. Multigrade engine oils became widely available in the 1970s where they combine the benefits of remaining fluid at low temperatures but retaining adequate thickness to protect the engine at operating temperatures. The ‘xxW’ portion of multigrade viscosity designation described the low temperature fluidity of the oil. Diesel engine oils typically meet the ’15W’ requirements giving protection to -15 degrees Centigrade. For colder climates ’10W’, ‘5W’ or even ‘0W’ (for arctic conditions) may be used. The h
