What is the thickest diesel engine oil?

  What is the thickest Diesel Engine Oil? Thickness of an oil usually depends upon the grades. Oil grades are related with the performance of oil product’s performance which is found at operating temperature. Diesel engines are commonly rated between 15W-40 and 5W-40. The number which comes before W stands for the thickness of the oil when it is on the cold temperature and the number which comes after W reflects the oil’s thickness when it is at normal operating temperature. The thickness of an oil is more commonly referred to as viscosity grade. Viscosity is a measure of a fluid’s resistance to flow. It actually describes the internal friction of a moving fluid.in simpler words oil viscosity refers to how easily oil flows at a particular temperature. The oil that has lower viscosity are thinner in comparison with the oils that has higher viscosity grade. Higher the viscosity thicker the oil. It is believed that thick oils are better at maintaining film strength and oil pressure at hig