Air filter part numbers C or CW ?
 

Anyone know the background to some of the original GM air filter element codes? Mainly when elements carried either the C or CW code and worked for the same application? Other types seemed to do the opposite and resorted back to C only, or never gained the W, for whatever reason.

One example being the common A212CW filter from the early 70's, later being offered as A212C, but then the same application resorting back to A212CW, and subsequent updates referring to all as A212CW as the A212C had been replaced by it.

Some early variations were for the open element types requiring a different wire mesh, possibly gaining the W over the closed element types of same size. But years later, became one and the same.

For that same example, I have original GM air cleaner label for 1977 Firebird with A212C only. I also have an original GM air cleaner decal for 1978 Firebird with A212CW. References to the types, printed years later, call both A212CW and no mention of the A212C.

Maybe it has to do with the supply source? At that time period I don't know if GM sourced air filters externally or if they were being made from within.

The 212 will fit in a 78 TA. Replacing the 542. I saw a nos one at a swap for cheap. Thought I’d see if it fits, it does.

This source said that the "W" originally stood for oil wetted and later stood for white.

Excellent information. I was googling for ages and never came up with anything except discussions on the mesh.
Still seems vague in application. For instance the parts manual on a 77 Formula with 350/403 Olds calls for the A212CW element, yet the Keep your GM car transfer says A212C only. By 78 it had become CW.