Preventive maintenance (PM) is a strategic
component an effective fleet management program designed to ensure vehicles and
equipment are fully functional and safe to operate. Regularly
draining and replacing engine oil is a common PM action performed to maintain
engine health and prolong engine life. The interval at which oil should be drained and changed depends on the
rate at which it degrades and/or becomes contaminated. Intervals that are too short result in
unnecessary PM costs and downtime, while intervals that are too long increase
engine wear and the likelihood of engine damage.
The purpose of this project was to further
the previous NCDOT research regarding the rate at which engine oil degrades by
expanding the equipment classes and geographic region studied. The
Spectro Scientific MicroLab 30 on-site oil analyzer was used to analyze the
physical and chemical properties of fresh and used oil samples of Xtreme
synthetic blend 15W-40 oil and Rotella T6 5W-40 synthetic oil. Samples of used oil were collected and
analyzed from 15 machines that consisted of trucks in classes 0205, 0210, and
0212; backhoe loaders in class 0314; and excavators in class 1854. Oil drain intervals for these machines were
extended beyond the typical schedule and changed based on a comparison of
analysis results with the established threshold values. Oil samples were collected at 3000, 6000, and
then every 1000 miles for the trucks.
The backhoe loaders and excavators were sampled every 100 hours.
Analyses of the used oil sampled from the
NCDOT equipment showed that the oils degraded chemically as the oil aged, and
viscosity degradation and/or contamination was not observed. The results indicate that the oil drain
intervals for the studied equipment can be conservatively extended. It was conservatively estimated that over
$530,000, over 11,800 gallons of oil, and over 4,400 hours of downtime can be
saved annually.
