Up through 1955 Task Force trucks, the oil-wetted "silencer and flame arrester type" metal-mesh filter element air cleaner was standard equipment (on all 3100-3900 Advance-Design trucks and many 1955 Task Force trucks up to 4000 series) .
An oil bath filter was optional equipment on A-D 3100-3900 trucks.
One of two types/sizes of oil bath filters were available as standard equipment on A-D 5000-6000 series trucks.
It looks like all 1956 and later Task Force air cleaners were oil bath.
It is interesting to note that in 1958 the two types of standard oil bath truck air cleaners had different types of filter element fibers.
