Purpose of a winter grill cover?
 

When I bought my truck the previous owner gave me a winter grill cover. It's been getting cold here (anywhere from -10C to -20C) so I put it on. Maybe I'm missing something but I'm guessing its to keep some of the heat in?

I feel like an idiot asking this but what the heck [dummy] .

Yes, it's used when the outdoor temp is so cold that the radiator becomes overly efficient.

Mine always ran warm enough, but the thermostat cycling on the highway gets a little annoying. You had to keep chasing the temp gauge with the slider on the heater controls. I had one laying around from my '85 gasser, I put that on this year and it really calmed the thermostat down. You can just set the heater controls and forget them.

Since I have changed my radiator I only have one change in temp- when the thermostat first opens and you get the cold coolant from the radiator. You should think about it. [roll]

The radiator was changed in '03. The new style thermostat is supposed to be better at keeping a stable temp, but I hate to mess with a system that is keeping the engine cool and not leaking.

On the way home tonight I was thinking about putting the piece of card board in front of the radiator. Then I started to wonder what that would do the the effectivness of the intercooler. Just wondering if you notice any difference in EGTs with the winter front?
I got home and couldn't find a piece of cardboard so I guess I need to stop and pick up a case of beer errrrr.. diet coke tommorrow.

Oh yeah, EGT's rocket up very quickly with the whole front blocked off. Normal driving is not a problem, but if you want to play a little it can be annoying. When I open the "gills" I can play pretty hard with the water/meth going.

For a working truck, you can follow the recommendation in the owner's manual: 10% of the grille area is to be left open.

At work we have a couple old Ford L9000's that run really cold, when we make cardboard fronts for them we hack out a hole about a foot square in the middle of the cardboard. You don't need one that big, and 8" hole ought to give good airflow.