Doctors warn it’s better to catch health problems early through routine screening than to wait for symptoms. The same approach applies to caring for diesel engines. Fortunately, maintaining diesels requires less effort than keeping up with our health. Regular oil changes and routine oil monitoring prolong the life of an engine by helping technicians detect problems before parts fail.
Some boat owners might extend service intervals to try to save a few bucks. But metal particles from wear, soot, dirt, water and other contaminants that accumulate in the oil grind metal. The longer that oil is in the engine, the faster parts wear, costing more money for repairs over the long run.
“Those particles and contaminants also accelerate oxidation,” said David Cline, product manager of oil filtration systems for Parker Racor. “As it oxidizes, oil thickens and becomes less effective at start-up, causing metal-to-metal wear.” Those few seconds after start-up — before oil has had a chance to flow throughout the engine — are responsible for much of an engine’s wear.
Oil viscosity is based upon standards set forth by the Society of Automotive Engineers. SAE 30 oil, for example, flows more easily than “heavier” SAE 50 oil. Oil also thickens as temperature drops. Prefixes such as 10w denote cold-weather starting viscosity — 10w40 oil acts like 10-weight oil when cold, flowing readily between the moving parts, but then provides the protection of 40-weight oil at the normal operating temperature.
Engine designers might choose heavier oil to stand up to pressure where parts press against one another, but they also know lighter oil creates less internal resistance, increasing usable horsepower and fuel economy. Balancing the two requires oil that hasn’t been thickened or thinned by oxidation or contamination beyond what’s expected within suggested service intervals.
Oil also does more than lubricate. “Injectors are often operated by oil, so they’re quite susceptible to dirty oil,” Cline said. “Turbochargers have very little tolerance for oil contaminants too.” As engines produce more horsepower from a given configuration, they place more pressure on parts that the oil is supposed to protect. Pistons are cooled with oil, heating it and accelerating oxidation.
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