What is the yellow psi range, and what does it mean?

• A. (0-20 PSI) indicates clean
• B. (20-35 PSI) means elements must be changed at the end of operation
• C. (35 PSI and UP) means elements must be changed at once
• D. (15-25 PSI) indicates a minor fault

Answer: (B)

The main idea being tested is how to read the filter element condition from the pressure drop. The yellow range corresponds to a 20–35 PSI differential across the element. In this band there’s a noticeable restriction from accumulated contaminants, but it’s not an immediate failure. Plan to replace the filter elements at the end of operation (or at the next downtime) to maintain fuel flow and prevent a bigger drop in performance. If the reading climbs into the red range (35 PSI and up), that signals you must replace right away to avoid performance problems or damage. This color-coded scheme helps you time maintenance without guessing.