Haul-truck engines at North American Coal's San Miguel Lignite Mine near Christine, Texas, have worked with Chevron Delo 400 Heavy Duty Motor Oil SAE 15W-40 since 1997. Working 20 hours a day, six days a week, the Komatsu 330 M 100-ton transports deliver over three million tons of coal per year. It's a brutal environment for the Cummins KT 38 power, but even with oil-change intervals stretched to 500 hours, they consistently approach double the expected life.
Several of the Cummins KT 38 diesels have worked 30,000 hours before their first overhaul (the industry standard is 16,000 hours). According to Wade Sivertson, San Miguel Mine's maintenance planner, that saves about $85,000 per engine.
"The people at the San Miguel Mine go to great lengths to ensure that they get good quality oil samples, and capture relative operating data in detail—things like engine hours, fuel burned, add-oil quantities," says ChevronTexaco's Donnie Thweatt. "They do it right."
Sivertson decided to overhaul No. 348 when the truck's engine reached 36,258 hours. Thweatt coordinated a study through Southwest Research Institute (SWRI), an independent, nonprofit research lab with an international reputation in fuel and lubricant analyses. The report indicates that the engine's components look nearly new. Pistons are remarkably clean, cam follower rollers are in excellent condition, and ring group deposits are minimal.