Covered grill and outside temps

[littlebitfarm]

I have foam insulation on my grill and it has certainly helped my MPG. Finally starting to warm up now. I know at some point I need to uncover the grill. My trip to work is only 4 miles. I'm not worried about the car overheating in 4 miles (am watching the temperature gauge). I actually got 93.4 MPG on the way home!!! 

 

Today is a 25 mile trip and a little cooler. I'm thinking maybe I should uncover some of the grill? I was thinking about taking out the piece of insulation that covers the middle third (runs width wise) of the upper grill and see what that does for me. 

 

Is there any reason at all to uncover the very bottom grill?

 

 

[plus 3 golfer]

If you use a/c, I'd uncover both grills completely as you want to be able to effectively remove heat from the condenser. Otherwise, the compressor may work harder and use more energy (similar to when the ambient temperature is higher and less heat is extracted from the condenser).  Also, the transmission and inverter coolers are behind the lower grill opening.  

 

Watching the temperature gauge is really not going to tell you much about coolant temperature unless the PCM initiates Stage 1 Strategy:  "Stage 1 of the strategy commences if the engine starts to overheat. The CHT sensor transmits a signal to the PCM, which moves the temperature gauge pointer into the red zone."

 

A better way to monitor coolant temperature would be to put the left display into Engineering Test Mode and monitor coolant temperature during longer trips when the ambient temperature is higher.  You should then be able to get an idea of how the coolant temperature varies with speed and ambient temperatures with the grill covers and without the grill covers.  I would remove the covers if the coolant temperature stays consistently above 100*C (212 F).  I have yet to find out under what conditions the cooling fans come one. I believe ptjones noted that he observed them on at around 215 F.  You certainly don't want the air flow to the cooling fans  restricted by grill covers.