Oil System 65 Oil Viscosity The viscosity grade defines the thickness of the oil. The oil must be thin enough at low temperatures for easy cold starts and thick enough to protect at high temperatures. An oil is not fully defined until both the API quality classification and the viscosity grade are specified. Choose the viscosity grade for the typical ambient temperature for the application. Multigrade oils have a broad range that suit operation in changing temperature. Only choose a monograde oil if the temperature is holding steady over a long period of time Volvo Trucks North America, Inc. recommends the viscosities shown in the viscosity/temperature table for Volvo engines.
For Cummins engines see your introductory package. Choosing an oil with a lower viscosity can help improve the fuel economy. However, if this is done, make sure the upper temperature limit is not exceeded. Also, with low viscosity oil, oil consumption can increase. W1000144 CAUTION Extra oil additives must not under any circumstances be added to any engine oil used. Additives such as break-in oils, top oils, graphitizers and friction reducing liquids are not necessary and may even harm the engine.