There is nothing wrong with oil bath air cleaners under the hood. However paper air cleaners are easier to service. I have been operating over the road trucks since 1964. Oil bath air cleaners were phased out in the late 60's and early 70's because no matter where they were installed, water would get in them and the oil would emulsify and the level would rise to the point that airflow was greatly restricted. The same thing happens with old farm tractors. If they sit outside in a driving rain, water gets in the air cleaner. The large cans on the side of some conventional trucks are vortex air intakes, not oil bath filters. They are very expensive and see limited use with owner operators who like chrome. Pleated paper filters have been the standard for many years. But under the hood on older vehicles where water is not a problem, it is up to the owner's preference. Maintenance is the key factor in either system
