During the Advance Design Truck years, two air filters were available when an order was sent to the factory. The base air filter (no extra cost) was the oil-wetted design from earlier years. The owner was expected to place a thin layer of motor oil on the filter media. Dirt particles would be caught by the oil as it passed through the mesh material. This metal mesh looks much like the material in a kitchen pot and pan copper scraper. The owner was reminded to clean the mesh every 2000 miles for it to be effective.
For an extra $5.00 an improved oil bath air filter came with the new truck. Most everyone who used their GM truck for work duties chose this filter. It required less maintenance and was more forgiving if neglected. GM recommended cleaning in kerosene each 100 hours or 5,000 miles minimum. Part of the filter media actually sets in an oil reservoir that has a pint capacity. The oil is slowly drawn up into the filter material and collects dust particles as the air travels to the carb. * NOTE: For best results use non-detergent oil. Dirt is not held in suspension with non-detergent oil and it settles on the bottom of the reservoir. At the same time held particles slowly sink toward the oil reservoir and accumulate at the bottom. Thus, this filter is always effective due to the oil upward movement. When the oil is changed in the filter pan or reservoir the dirt is also removed.
As with other manufactures air filters, they will cause fuel mixture problems when not maintained. A very dirty air filter will restrict air flow into the carburetor and result in increased fuel consumption.
Oil Wetted (above)
Oil Bath (above)
Oil Bath (above)
