Then find a way to jam it in there in front of the radiator. It helps the engine warm up much faster and in 2.5 miles might cut the time to operating temp in half, especially with engine running constantly. If it restricts the air flow to much the electric cooling fan will come on. In that case make the block smaller.
I just ran my pipe insulation today, with two (of 3) brothers in the car on Interstate at 60-70 mph. After 35 miles the temp had climbed to 205 max, thermostat opening at 186. I removed a small section of the pipe insulation and it never hit 200 degrees, just about perfect.
Can't remember if it was Bentley or Alvis but Packard had the grille vanes that adjusted themselves based on temperature. Just like the 18 wheelers here you see with covers for the radiator.
Cooling systems are designed for "worst case scenarios". Many modern cars. have flaps that restrict air flow to the radiator. The principle is the radiator can remove to much heat from the engine, wasting fuel to heat the coolant when that same heat can be saved by making the coolant hotter coming out of the radiator (as it does in summer).
Temps here today were in the high 30s at sunrise, climbing to 57 degrees at peak. When I had to much blocked I just coasted down to lower speeds and the temps dropped quickly.
FYI, the poorer fuel economy due to cold weather is not just due to the engine needing more time to heat up. It also includes the entire drive train. It stiffens up due to the cold, and offers more resistance, and therefore, poorer fuel economy. This includes:
belts and the devices the drive, like a power-steering pump (minimum effect)
transmission (thickened up lubricant)
One time that stayed overnight in the Virginia mountains on my way to Florida, the overnight weather was close to freezing. My vehicle got cold-soaked. The next day, even after an hour on the highway, my engine was still noticeably thirstier. Even when going downhill, where my fuel consumptions would normally drop to zero, the cruise control was still applying throttle to go downhill! By the time we were crossing the Georgia/Florida state line several hours later, ambient air temperature was in the mid-70s, and fuel economy on level roads was back to its normal high.
Yeah, cold-weather driving has a big negative effect on fuel economy. Everything stiffens up and offers more resistance.
2015 Audi Q5 "Progressiv" + S-Line + Scuba Blue, 3.0L V6 TDI
(Highest fuel economy for all Audi Q5s on Fuelly!)