All you need is a roll of masking tape, and you can isolate engine heat and gain heater output/MPG:
Things I learned from this:
-Scangauge shows a ~3 MPG improvement in town driving, real world results to follow
-Intake Air Temp increased to ~40 degrees above ambient, up from 10-15
-Upper intake is sufficient to prevent overheating, even while sitting in traffic on a 50* afternoon
-Cooling fan kicks on at 206*
-Less engine noise is heard with the lower grille blocked off. Because of less air rushing through engine bay?
I'll be using this setup until the spring equinox or until I start seeing temperatures over 215* consistently, but so far this seems like a great way to help enhance cold-start and heater performance and maximize MPG while winter is still around.