Machinist’s Mate "A" School Test 3 Practice Exam 2026 – Complete Prep Guide

Keeping the lube oil clean is the main idea here. Lube oil strainers and filters are there to remove foreign debris—dirt, metal shavings, rust particles, and other solids—from the oil as it circulates. Strainers usually sit on the inlet side and use a coarse screen to catch larger particles, while filters use filter media to trap smaller contaminants as oil passes through. This cleanliness protects moving parts like bearings, gears, and pumps from abrasive wear and helps maintain reliable lubrication flow. It isn’t about removing dissolved gases—that’s a different process—and a clogged filter can actually raise differential pressure and reduce flow rather than increase lubrication pressure. Water removal is typically handled by separate stages, not the basic strainers and filters.