21431831 Dimensions: Height:558 mm OD:280 mm ID:186 mm   21431840 Dimensions: Height:527 mm OD:180 mm ID:161 mm   21431840 21431831 OEM Alternative Part Number: NISSAN 165289Z00A.DONALDSON X011471.   Air Filter Maintenance Is Essential: The key advantages of regular air filter maintenance include: Improved performance - clogged filters can have a significant, detrimental effect on how your engine runs, hampering performance and reducing power output leading to a lowering of operator work-rate Lower emissions - because the air-fuel mix is finely calibrated, failing to maintain your filter will cause an imbalance and less efficient fuel use, contributing to greater emissions Prolonged engine life - the air filter traps the dirt and other debris that can cause wear to your engine. The actual size of the debris might be quite small but even those as small as a grain of sand can significantly damage the engine over time, with the potential for damage to pistons, rings and cylinder linings All these issues can be avoided by incorporating the replacement into your regular maintenance regime. The frequency at which air filters need to be changed will vary according to the engine model you run, and more importantly the environmental working conditions. Dusty and dirty environments and enclosed spaces raise the importance of checking the filter condition regularly.