I've been using Lund plastic grill inserts(JCW or Summit?) for
almost 2 years, best winter front device I've tried. Cost a little
more than cardboard, but works better too. I leave them on in
the summer too, because they filter bugs and rocks out from going on into the A/C, intercooler, and radiator. Every once in a
while I have to wash them off if I'm pulling a trailer on a hot day.
If I don't the temp gauge starts climbing. I'd rather have the
restrictions on the outside where I can see and wash them off.
However, if you pull a lot of weight in hot weather, you may have
to remove 1 or 2 of the 4 inserts.