Scheduling an oil change is as routine as getting your teeth cleaned. The service garage issues the next appointment when you leave on from the last. Changing engine oil every 3,000 miles assumes your engine is working the same way everyday of every week or every month. Not true. Whose vehicle is driven over the same roads at the same speed under the same weather conditions every day? You don’t go on blood pressure medication until your lab tests indicate a need, so why not test your engine oil to learn what’s going on in there? A simple test with some basic understanding help you target your maintenance dollar and even avoid breakdowns.
A sample of your engine oil can reveal a lot about what is happening under your hood. Diagnostics relate engine wear, leaks, cracks and pump failures. Most oil analysis will break down into three major categories: wear & contaminant metals, characteristics like water & air and an overall diagnostic summary of major parts.
In the oil sample, the presence of certain metals can indicate problems of engine wear. For example, high aluminum levels can imply piston, engine block, blower or bearing wear. Chromium in the oil can be symptomatic of compression rings or cams. Excessive copper could be from bearings, bushings or thrust washers. Wearing of the crankshaft, valve train, cylinders and gears may leave high levels of iron in the oil. Even tin is found in the oil resulting from worn engine parts. Just like a blood test the oil can really tell us what is going on inside.
Additive metals are and contaminant metals provide evidence of leaks or pump failures. Typically, air intake problems or coolant leaks will put excess silicon, potassium or sodium into the oil. Looking for contaminant metals doesn’t just mean an oil change but an air filter change and a coolant system assessment.
Physical characteristics of the oil sample can also help diagnose leaks, air intake system problems and over-used old oil. Water and glycol in the oil could mean a cooling system leak. Fuel dilution is when the air/fuel ratio is unbalanced, thus combustion is faulty and fuel leaks or injector problems should be investigated. Oxidation is measured in absorbance units and climbs as the oil ages. If the value is over 25, change the oil. Nitration is also measured in absorbance units. Nitration products are formed during the fuel combustion process and can be a good indicator of corrosion and oil deterioration. Another physical characteristic is viscosity – the way a fluid flows. Engine oil is carefully designed to operate at a given viscosity under a certain temperature. If the viscosity measure in your oil analysis is too thick or too thin you will need to change the oil.
The test results may sound complicated. Don’t worry about understanding every measurement; it is more important to get the test done and then watch for changes in the analysis next time you have it tested. The cost of an average oil analysis is around $15 and well worth it if you can learn how well your engine is running and target proper maintenance.
