The oil analysis is an important maintenance tool for vehicle owners. It is based on the monitoring of the physical and chemical properties together with the contamination level of the lubricant. Thus, through these properties, the condition of the engines can be assessed and recommendations can be taken on the future maintenance actions. The main part of the project work consists in collecting used oil samples for analysis purposes. The oil properties are monitored over a time scale and linked with the maintenance history of the particular vehicle in order to determine the variation trends of these properties and the factors affecting them. The wear metals contents of the oil have been trended as well as the physical properties. Cumulative values have been plotted for the wear metals. Statistical analyses of the test data especially for the standard deviations have been carried out; these have been used to determine the reportable and the alert limits and the moderate and the rapid trends. This study started in June 1998 and rolled on through to 2001. The collection and submission of oil samples for analysis purposes was solely the responsibility of the firms and companies participating in the project. In fact three companies were chosen at random and some 280 oil samples were expected to be obtained. However some way through, two of the companies showed sign of slackness and pulled out for reasons of staff earlier committed to the project leaving the company or otherwise. Ultimately only one company supplied the bulk of the oil samples. The advantage so derived is that a more thorough analysis was made possible with a substantial number of samples for the vehicles of that particular company.