Volant Primo Diesel air filters are made with 8 layers of the highest quality textiles pleated between a top and bottom aluminum screen, designed specifically for severe duty trucks. Each filter comes pre - oiled and ready for use. This design will allow the highest air flow rate possible and a very long filter life and service intervals of up to 40,000 miles depending on driving conditions. We recommend cleaning Primo Diesel air filters only when necessary. Inspect the filter every 12,00 - 15,000 miles to ensure peak operation.