The above reply got me thinking.
When someone who often contributes to this forum feels he can’t share an idea because it will get railroaded, maybe we should all try a little harder to be civil. I know many times I’ve responded a bit on the harsh side.
Don’t be that way.
I have had similar feelings. It was when I got an answer I wasn’t expecting, and I took it the wrong way. Yes, mcparadise’s response lacked tact, but sometimes we don’t learn anything new unless someone shakes things up a bit.
The guy who founded FedEx was told by his business professor that his idea for overnight delivery would never work. Imagine where he would be if he didn’t think outside the box.
I see the less than polite responses, my own included, as a discussion that kind of snowballs, gets a little out of hand as we may feel a little removed from OP’s question and respond without thought after reading several posts.
“circuitsmth” makes a good point.
I wonder if it’s really ineffectual. Granted, the bulk of the cooling is done by the radiator, and the thermostat simply won’t let coolant flow there 'till it comes up to temp.
But my understanding is that a non-negligible amount of cooling–particularly W/R/T aluminum blocks–was done by simple convection of heat off the block. (I’ve even heard that early Al engines did not take kindly to being allowed to get all dirty/greasy.) IF this is the case, limiting airflow in the engine compartment ought to speed warm-up.
(I just don’t know how significant this would be…how much cooling is done by the actual block.)
circuitsmith in northern MN. you will see all kinds of cars + p/u’s with weather fronts on in winter. -30 , -40 below. only way to keep motor warm.
mcparadise may have over stated the point. You are not craze, but you may have been ill advised or connected one too many dots coming to your conclusion.
I will suggest that you are not crazy because you came here to find out what others had experienced. That is not crazy. What would be crazy is to ignore the advice here.
Note: mcparadise has been around here a long time of offered a lot of great advice. I have learned a lot from him. Of course he has gotten off track a few times like we all have.
I don’t think it will make that much difference in DC. In North Dakota, maybe. But not where you live.
I have blocked my radiator in the winter for quite some time now but it’s difficult to test with all the other variables if it does any good. However, I would like to point out that with my 1996 Honda Civic with 224,000 trouble free miles that the winter time mileage is in the low 30mpg while summertime I get 40mpg. So is it the gasoline formulation that has less BTU’s in the winter… or is it engine heat loss? I need a cozy for the engine compartment to test. 
I live in Detroit metro, Michigan.
“is it the gasoline formulation that has less BTU’s in the winter… or is it engine heat loss?”
It’s the gas plus longer warm up times and aerodynamic loss from higher air density.
In the mean time, I’ve compared the average of two fillups without the cover to two with the cover and saw an increase of 0.75MPG (27.25 to 28MPG), in spite of a small drop in average ambient temp.
All fills were ~1/2 a tank at the same pump with no topping off.
All the trips were short, mostly stop and go, 20mi or less, driving the way I normally do, which is pretty gently.
Now, who will be the first to say my data is meaningless and I’m wasting my time?
When I lived in North Dakota we all did it. Some would stick a piece of corrogated cardboard in front of the radiator, some would hang a piece of blanket. Left open, the engine would not get to running temp at all after sitting all night at -40 degrees and being driven in -30 degrees!
I remember seeing a film back in the 1950’s about the changes in the sociology of a town in North Dakota after oil was discovered. In some of the scenes shot in the winter, many of the vehicles had the radiators partially covered.
Early Volvos had louvres behind the grill which could be controlled from iside the car.
Before we had viscous and electric cooling fans you could buy those padded leatherette snap-on covers with small panels that could be opened with high engine loads. I kept those on my 1966 Chevelle Malibu, my 1976 Ford Granada, and also on the 1977 Dodge Colt, since the engine was so puny it hardly generated any heat in the winter.
Any upholstery and convertible shop can make you one of these snap-on grill covers for winter use. I paid about $40 each to have them custom made. J.C. Whitney might have them for popular models.
Agree they are very popular with truckers in the North.
Same memory from the 50s. I think it was to keep snirt out of radiator and off the engine. For those of you saying Huh?, snirt is a fine wind-blown powder of dirt and snow. It gets into everything - even suffocates cattle in a blizzard. Melts much slower than snow and leaves mud behind.
I used to do this with a 95 Dodge Dakota. I don’t know if I saved gas, but the truck did warm up a little faster.
Ed B.
Yup. And we plugged the engine heaters in at night. Apartment complexes came with assigned (numbered) parking spaces with sockets on posts. The renter had a switch in the apartment to turn his/her socket on at night. It’s truely a different way of living.
I remember after seeing the film that I thought I would like to live in North Dakota. My Dad, who had spent a couple of years in Minot, N.D. wasn’t so sure I would like it.