Komatsu PC450-8 Operation & Maintenance Manual page 326

MAINTENANCE PROCEDURE
7. After replacing the filter cartridge, add oil through oil filler
port (F) so that the oil level is between the H and L marks
on dipstick (G).
8. Run the engine at idle for a short time, then stop the
engine, and check that the oil level is between the H and L
marks on the dipstick. For details, see "Check Oil Level in
Engine Oil Pan, Add Oil (3-114)".
9. Install cover (1).
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MAINTENANCE