Dallas-based Stevens Transport, a refrigerated TL carrier with 1,600 trucks is now approaching 200,000 miles between oil changes and the fleet's maintenance management staff is confident these super-long oil drains are safe and not harming engine life, Today’s Trucking reports. The Stevens fleet is made up of Kenworths and Peterbilts, all with Cat C15 engines. A 6-oz. oil sample is taken about every 30,000 miles and sent to Holt Caterpillar's lab in San Antonio. The oil analysis on each engine identifies parts per million of brass, copper, aluminum, and other wear materials. It also shows if there's any antifreeze or fuel dilution, according to Today’s Trucking. Stevens had been changing oil and filters every 30,000 miles, which is five or six times a year in this extremely high-mileage fleet. Under a test program started in March 2003, Eric Smith, the company's director of maintenance, began evaluating a new type of bypass oil filter that filters oil down to the 1- to 2-micron level and also boils away non-solid contaminants before returning the oil to the crankcase. After more than a year of tests during which Smith saw a dramatic decrease in the number of oil changes per year, Smith decided to change the entire fleet over to the new system, doing about 50 engines per month. More than 700 installations have been completed to date, and Stevens is projecting an 80-percent oil maintenance cost savings per truck per year. The filter is sold directly by the manufacturer, Oil Purification Systems Inc. Karl Klein, Stevens' service manager, said the OPS-1 bypass system takes an oil line off the pressurized side of the engine, going directly to the filter. It has a low flow rate—only four to five gallons per hour—which allows the oil to be filtered down to 1 to 2 microns through a small cellulose bonded filter. Oil then passes into an evaporation chamber heated by an 89-watt 7-amp heater that heats the oil to 195 to 210°F in order to evaporate off any liquids. Cleaned oil is then returned to the crankcase virtually soot and glycol-free. The OPS units are about the size of a coffee pot and can be mounted wherever it's convenient—typically on the firewall. The two-piece system takes about an hour to install, according to Smith. Based on its experience to date, Stevens' management is already saying it might be able to extend vehicle life one to two years and do it without overhauling engines.