The ability of modern diesel engines to operate successfully with high soot loadings in their lube oils together with extended drain intervals has been achieved through the use of a range of techniques to condition the oil. Full flow filters, bypass centrifuges, heat exchangers and a range of sensors and complex monitoring systems have all been added to engines to ensure that the oil is delivered to the lubricated surfaces at the optimum temperature and cleanliness. Traditionally each of the devices in the lube oil circuit has been considered, designed and purchased separately from different suppliers.The current trend throughout the automotive industry to reduce the number of first tier suppliers can be seen as a good reason to combine the elements of the lube oil circuit into a single unit, however this is a short sighted approach. There are very serious gains to be made in oil conditioning performance, energy consumption (and hence fuel economy) and cost reduction by taking a full systems approach from the outset. Applying the systems methodology to oil conditioning can result in the whole unit being of greater value than the sum of its parts.