Understanding Oil Contaminants

In the past two months I have had numerous calls about fuel filter contamination issues. They usually start with my fuel filters keep clogging up or I have oil in my fuel because I see black residue in the fuel filter. Many of the callers are requesting that the fuel be analyzed to identify the problem. While fuel analysis is available it is costly and requires special containers to protect from leakage during shipping to the lab. (Never send fuel samples using glass jars or plastic bottles that degrade and rupture in transit) Fuel analysis is usually used by companies with underground tanks to ensure the fuel is not contaminated or not of the cetane levels they are purchasing. There is no need to spend $$$ on analysis to identify the problem. There are a few types of fuel contamination that will clog that you can identify with a plastic tube and some white paper towels. Dip the tube down to bottom of tank, place thumb over end and pull it out. The fuel will be in the tube with contaminants. If tube is clear, look for particles or discoloration in fuel or release some fuel on to a paper towel. Hard black tar like substance would be asphaltene, dark greenish/brown slimy particles would be bacteria and yellowish soft particles would be wax. Once you identify the contaminant I suggest you google the problem and start the removal process. Each contaminant has a different solution and may require tank removal and flush to fully solve the problem. I can tell you that the use of bio-diesel has increased the number of issues with bacteria and asphaltene in recent years.

Keeping with the fuel theme, here is a common question I receive. My oil sample results were showing high fuel dilution that caused my viscosity to drop a grade. I added a viscosity stabilizer to bring the viscosity up to correct grade. Am I putting my engine at risk for failure?

While the viscosity stabilizer will bring the oil back up to the proper grade, you are just masking a fuel dilution issue that eventually will cause serious damage to the engine. Bear in mind that most oil analysis labs will not perform a Gas Chromatography test if the viscosity is within the parameters for your grade of oil. They will report a < 1% level based on the viscosity level without actually testing for fuel dilution. Therefore you would never know you have fuel dilution that is eroding the wear metal additive package in your oil that protects metal to metal wear. Gas Chromatography will report the actual level of fuel dilution in spite of the viscosity levels. I have seen fuel dilution at over 10% with a viscosity of 14.5 on a SAE15W40 oil (12.3-16.2) that would not have detected a serious fuel contamination issue. I find it is always best to fix a problem rather than mask it to avoid engine failures.

It is inevitable that some fuel will contaminate the oil during normal operation. The fuel mixes with oil on cylinder walls or bypasses rings. This usually has little to no effect on the oils condition. But a leaking injector or faulty injector seals that allows excessive amounts of fuel to contaminate oil can cause very costly damage. Too much fuel in one cylinder will result in unburned fuel and additional soot and too much fuel in oil lowers viscosity and reduces lubricity. Sampling oil regularly will identify a fuel contamination issue and save you $$$ in the long run.

If you have any topics or questions for this column please email to me at: [email protected]