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If mechanics simply discard filter elements, they lose a valuable way to check engine conditions. Cutting open filters, examining them and documenting the observations provide additional information that complements results of oil-sampling programs. By opening the canister's outer steel shell with the right tool, mechanics will expose two media types. All filters have an oil path that first enters a flow-through media stage designed to capture dirt and inorganic contaminants. Limited oil amounts are then directed through a second media, designed to remove sludge. By examining both filtration zones, mechanics can quickly evaluate engine condition. Record keeping is an important part of the examination procedure. Mechanics should first estimate and record the filter's degree of "plugging," then record the color of the particles trapped by the filter media. Mechanics should also note the condition of the media pleats. While visual filter inspections are no substitutes for chemical analysis of drain-oil samples, they can provide helpful and timely information. A filter/engine-condition troubleshooting chart is also included.