Analysis of used oil can be a very useful tool. Most oil analysis is done on used engine oil to determine the condition of the oil and from that to determine, at least to some extent, the condition of the engine. Basic used oil analysis measures the viscosity of the oil, the presence of fuel,  the presence of coolant, and measures the amount of the various additives in the oil. There are several reasons to use oil analysis and several ways to use it.

One reason to use oil analysis is to determine optimum oil drain intervals. Using oil analysis can help zero in on the right drain interval so oil is changed before it is depleted and oil analysis can help determine if oil change intervals can be safely extended. Sampling an engine when it would normally be due for an oil change will show if the viscosity is still in grade, if there is fuel or coolant in the oil and if the additive package has depleted or is still effective. If the analysis report shows that things still look good at say 10,000 miles on a truck engine, the oil can be run further and re-sampled at 2,000 mile intervals and keep going so long as the labs keep showing the oil is still not de-graded, contanimated or depleted. In this way the optimum drain interval can safely be determined and not just a guess. For a fleet of identical trucks, this process can be conducted on a single truck and the resulting optimum drain interval can be established for the fleet.

Another reason to analyze oil is if there is a change in the normal operation of an engine. If the oil level 'grows' it is important to determine where the additional material is coming from. More than likely it is a bad fuel injector leaking unburned fuel into the oil or coolant from either a hole eaten through a liner or a deteriorated or broken o-ring seal on the liner, or a leaky head gasket. In any event, fuel or coolant in the oil is a serious condtion that analysis of the oil can identify. 

Doolittle Oil offers oil analysis through Analysits Inc. Analysits Inc is an independant lab not affliated with any oil or equipment company. They have no bias in reporting accurately the condtion of oil sent to them for analysis without regard to who made it or what brand of engine it came from. We think this is the best arrangement. I

information on oil analysis and Analysits Inc