Does anyone know the efficiency rating of the Napa premium air filters? I'm looking at either the Napa premium or purolator regular air filter for our cars. The napa premiums look more plush and thicker. The regular purolator is more flat paper like. Purolator has on the box 96.5% efficient. I can't get any data on the napa premium. The napa's cost me $20, the purolators $10. Seeing if it's worth the extra cash. I change my filters every 2nd or 3rd oil change. so 20-30k air filter intervals. We live in the city, no dirt roads or anything like that. Just looking to keep the family cars in tip top shape and save money where I can.