The main benefit of a properly designed and selected oil filter is that it removes most of the particles that cause abrasive wear on the gears and bearings.  For the oil to also be properly filtered, it must pass through the filter under pressure.  The use of an optional oil filter will extend the service life of the gear drive under most circumstances, but regular oil sampling should be done to ensure adequate lubrication is in place. Although the main causes of premature failure in cooling tower fan drives are low oil level or poor oil quality, not abrasive wear.  Oil filter elements require periodic replacement and the external plumbing increases the potential of an oil leak. On the other hand, the Amarillo Gear Service Unit (GSU) oil filtration cart is unique and will extend the interval between oil changes.  Its special oil filter media does an excellent job at capturing particulate down to 3 microns and water. Visit www.amarillogearservice.com for more information on this product.