Question: Big contractors are motivated to stretch the time between oil-change intervals because trimming the number of oil changes on each machine in a large fleet adds up to big bucks. What's the payoff for smaller fleets, and how do you probe the limits of oil life without risking engine failure?
Answer: "The big advantage is in the production you gain," says Steve Fallert, equipment manager with Bloomsdale Excavating. He extended basic service intervals on 120 pieces of equipment from 225 hours to 350 hours three years ago. "That's hard to measure, but the labor savings alone makes it worth looking into. Why, we cut 83 oil changes out of our first big job at 350-hour intervals (a seven-month job moving 2.3 million cubic yards). And it was all overtime that we saved—we did all of our service work on that job during the second shift."
After three years changing oil consistently at 350 hours, Fallert is convinced that there are no hidden penalties in terms of shorter component life due to less frequent oil service. And he estimates Bloomsdale saves more than $12,000 per year on oil, filters and labor. He says increased uptime and shop productivity raise the total annual savings closer to $50,000.
"With the quality of oils available nowadays, even Cat is talking about extending oil drains," Fallert says. "We proved to ourselves that we don't need the big margin of error we had when we changed oil every 225 hours."
Fallert says oil-analysis results never showed an increase in wear. Last winter, he confirmed that longer oil life isn't cutting into engine life. Bloomsdale mechanic, Bob Lurk, rebuilt the Cat 3406 engine from a D8 that had been serviced at 350-hour intervals for 6,000 hours of its 11,000-hour life.
"We looked it over carefully to make sure there wasn't a lot of soot buildup," Fallert says. "The oil pans, the heads, the interior part of block—it was as clean at 350 hours as any engine we've rebuilt that was serviced at 225 hours."
Careful analysis confirmed that there was virtually no difference in wear in cylinder ring lands, piston skirts, or crankshaft journals. Despite this evidence of engine oil's durability, though, Fallert remains watchful.
He managed the transition to 350-hour service intervals very carefully because Bloomsdale's reputation as one of the area's leading excavators is built largely on the reliability and cost-effectiveness of machines under Fallert's care. The huge earthmoving job in the St. Louis area was a perfect test bed.
"I waited for the Gravois Bluffs job before trying to extend drain intervals because I knew we would be getting lots of hours running two shifts, we would have a couple of mechanics on the job, and we would be keeping a very close eye on that equipment," Fallert says. "We also had a good variety of equipment working out there. We got experience with longer drains on Cat's 3400 series, 3300 Series, and 3100 series engines, and the engines in our Volvo articulated trucks."
Mechanics pulled oil samples for analysis at each oil change. Fallert says the analysis results scarcely changed, even as they increased oil life in 25-hour increments. Quantities of contaminant in the oil—iron, aluminum, even silica (dirt)—never increased, and viscosity remained virtually constant as oil life gradually increased. Before the seven-month project was complete, they had taken service intervals out as far as 400 hours.
"The numbers looked good, but we backed down to 350 hours in the end—I'm not that much of a gambler," Fallert says. "We wanted to see what happens to the engine over the long haul when you're servicing at 350 hours. And we're just reaching that stage now."
All the evidence is pointing toward a move to 400-hour service intervals. Oil analysis numbers have been consistently good. Teardown analysis shows normal wear patterns on at least one engine serviced at 350-hour service intervals. And Fallert has been able to schedule regular service on all other components in the fleet at manufacturers' recommended intervals.
"If we're going to do it, we'll probably bump it (engine service) to 400 hours within the next four months," he says. "We're starting a large project this spring, and I want to test the service intervals on another big job where oil changes will be coming frequently and we can keep an eye on the situation."