Understanding Oil Contaminants

Tom Bock
September 2018

It’s not very often I get a question from a driver with 49+ years behind the wheel and over five million miles on the road, but I received one this month from moverman124 ("SAFE & ON TIME SINCE '69"). His question was about a friend of his that has a 2006 Detroit Diesel Series 60 and he changes the oil every 10,000 miles, and he wanted to know if it is too soon to change oil at that rate. At what mileage interval should it be done to get the proper usage?? He runs a 53' box trailer, has around a million miles on said truck and drives about 100,000 miles a year. This is difficult to determine as there are numerous factors to consider when determining the useful life of motor oil. The conditions you drive in, on road/off road, extreme hot/cold temperatures, weight of loads hauled, stop and go/ over the road and probably the biggest factor is condition of engine (blow-by, fuel injector leaks, antifreeze contamination, overheating etc.).

I know from experience with bypass oil filtration systems that oil can maintain the properties required to protect engines for an extended period of time. So, in order to receive the optimum value from the oil the only way to do so is to sample the oil at every drain interval to evaluate the contamination level and determine the oils quality. While the 10,000-mile interval used by moverman124’s friend may be too soon causing additional oil maintenance expenses, if the engine is worn and fuel dilution or soot generation is contaminating the oil it may be the right interval. That being said if engine is properly maintained and his friend drives over the road with little to no excessive stop and go traffic, while hauling average loads, I think he is changing oil prematurely and wasting $$$$ each year. Again, the only way to be sure is to sample oil with a reputable lab that provides report on wear metals, contaminants, viscosity fuel dilution, soot, total base number, oxidation and nitration. These extensive samples reports usually cost $30-35 and are well worth the expense to determine the interval that is right for your vehicle. For example, if moverman124’s friend can change interval to 15,000 miles supported by oil sample results he would save approximately $1000 per year plus reduce downtime for oil changes.

You may have noticed I mentioned stop and go traffic above which has a major effect on the oil change interval. If you drive in major cities and spend the majority of your time idling etc. you might want to consider setting your oil change interval with either an hourly usage or fuel usage interval. I can tell you from past experience adhering to a mileage interval does not work for local delivery vehicles etc. The company policy was 10,000-mile oil changes but half my fleet didn’t put on this amount in a year, but they idled in New York City traffic 8-10 hours per day. Subsequently engines were failing as oil degraded prior to hitting the 10K mark. After the company analyzed the failures it was determined that the intervals would be determined by fuel usage as the data was recorded weekly for tax purposes and would not require installing hour meters in all the vehicles. The failure rate was significantly reduced with the new policy. I only wish the company had instituted an oil sampling program to identify potential engine issues before any failures occurred so proper repairs could be made.

If you have any questions or topics for this column, please send to [email protected] with subject line Movin' Out Question.