[Lawrence Coppari]

I made temperature measurements regarding this several years ago. I have a MAF with cone filter right by the coolant reservoir. I attached a thermocouple to it (in the pleats of filter) and found that when the car is moving about 20 mph, there is less than a 2 degree difference between air there and outside air. When you stop the car's motion, the runup in temperature occurs very fast but falls right back off once car gets moving. That corner of the hood gets a lot of fresh air.