Is oil analysis more beneficial for a combustion engine or a hydraulic system?

In engines, oil analysis can provide information concerning the condition of the air intake system by monitoring the silicon (dirt) levels in the oil. The levels of iron and aluminum can warn of piston and cylinder wear before a major failure occurs. Bearing wear rates can be determined and action taken before the crankshaft becomes badly scored. Fuel dilution, anti‑freeze leaks and water entry can be detected while they are still minor problems. The levels of contamination and combustion soot within the oil can indicate a restricted air intake system, ineffective oil filters, poor combustion or a rich air/fuel ratio.

In hydraulic systems, transmissions, gearboxes, differentials and other lubricated systems where combustion does not take place, the analysis of oil samples should also be done on a routine basis. High levels of aluminum can indicate a potential pump or converter failure. Transmission slippage is often indicated by high levels of copper, while high chromium levels can reveal scored hydraulic cylinder rods or gear and bearing wear.

The cleanliness of hydraulic oil systems is extremely important because of the very close tolerances that exist in the pumps, control valves and between the pistons and hydraulic cylinder walls. In fact, 75percent of hydraulic system failures are caused by contamination through dust, dirt and condensation moisture. Therefore, oil analysis should be performed on a regular basis to monitor contamination levels.

Oil analysis can also be used effectively to determine the proper oil drain and filter change intervals in all types of lubricated systems.

To properly interpret the analysis results, the laboratory should be advised as to the viscosity and type of oil, the hours or miles of service, and the make and model of the component or system from which the sample was taken. This information should be printed on a card usually provided in the oil sample carton.

Oil samples should be taken on a regularly scheduled basis and should only be taken after the lubricating system or component has been operated long enough to reach operating temperature. This will ensure that the oil has been thoroughly circulated and will result in an oil sample that is truly representative of the oil in the system. The oil sample should always be taken at the same point in the system, such as from a valve mounted on an oil return line before the oil passes through the filter.

The sample container should then be sealed immediately and sent to the laboratory as soon as possible.