Yeah...for you guys up THERE I guess a winter front is pretty much a MUST-

but last time I asked for one--down here in the lower 48- was told Freightliner Century & Columbia--is never suppose to be run with one......

scratches head.....Now why is that? Bob! hey Bob? why is that? you know anything bout that?

-Fresh air huh? I'll try that, I was on recirculate.
-Where is the filter Bob? Quick b4 I tear the whole truck apart.

Because you aren't supposed to block the charge air cooler in front of the radiator, will lead to a massive loss of power.

As far as KW goes, there is NO filter that I am aware of, I have had the system apart to change the fan motor and the heater core and NEVER saw a cabin filter or a bunk filter.

There is a fresh air opening on the right hand side behind the air cleaner and it goes straight in the system.

There are after market filters available, but I don't have one.

As far as the drivers window fogging, I think its because the window is warm and when I get in the cold comes off me and fogs it up, been living with it so long it really doesn't bother me.