Cold Weather Vehicle Question

A few years back we moved from the relative warmth of California to the sub-freezing temperatures of Northwest Montana. Where we live now the temperature from Nov through Mar can run anywhere between -15 and 40 degrees F.

I’ve noticed that fair number of SUVs and Trucks (not talking about Semis here), and even some cars have those vinyl or cloth covers over the front end of the vehicle where the radiator sits. My guess is that they are restricting the amount of freezing cold air passing through the radiator in order to keep their engine at normal running temperatures. I have a few questions about these folks and their vehicles:

  1. Is this a common practice in other cold weather areas of the US?

  2. Why? If your vehicle has a properly working thermostat wouldn’t it restrict the flow of cold coolant through the engine in order to maintain the proper engine temp? Is there a limitation on how well a thermostat works in very cold weather?

  3. If your engine temp is running low much of the time it can impact the efficiency of your engine, but if my engine temp it right about the middle between C and H is that okay or do I need to have someone assess whether the engine is running too cool? I’ve noticed that my gas mileage gets worse in the winter but I figured there are lots of reasons why that might happen.

  4. Since all of these folks seem to think they need to restrict the airflow should I think about adding one of these covers (or whatever they are called)?

  5. Could it be somehow related to the fact that many people around here have diesel cars and trucks?

Any advice would be appreciated. BTW, both of my vehicles are modern (2008 4-Runner and 2010 Tundra).

What you most likely seeing is what is commonly referred to as a bra. It’s typically there for looks/style and to protect the nose of the car form road debris. Some people will block the airway to the radiator with cardboard (or some other method), but they typically do that to get it warmed up faster.
Modern cars (at least the last 3 or 4 that I’ve had), have been in the normal operating temperature within 2-4 miles of driving from a cold start.

Thanks JP. These aren’t bra’s… they are square or rectangle and only cover the front where the radiator is.

I thought about whether it would help warm up the vehicle faster, especially if parked outside, but wouldn’t it lead to the engine temp running too high after a while?

In cold weather, even with most airflow in front of the rad blocked the engine won’t overheat. The point of blocking airflow is so that there’s more excess heat to run through the heater core.

Ahhh… that makes sense.

You saw them a lot more back in the day when the fan was connected directly to the fan belt and turned whenever the engine was running. Now, with transverse mounted engines and thermostatically controlled electric fans the fan doesn’t turn until the engine is warm anyway.

These grill covers are fairly common on diesel semi tractors that do long hauling across the country.

I made my own apron to fit across the grill of my GMC pickup. I only use it it really cold temps from -5 to 25 degrees. The reason is that in short distances, the heat comes up faster than with just the T-stat operating. Eventually, it would come up to temperature anyway. The kid likes heat. My windshield likes defrosting, and an engine at temperature gets better mileage-by far. There’s enough air flow getting up there to the radiator so that even 40 degree plus will not overheat it. If I could put cardboard right up against the radiator, it would do a better job. However, I don’t want anything, even cardboard, bumping and rubbing that radiator.

Don’t those people use engine block heaters anymore? When I lived in Minnesota for two months 30 years ago, block engines were common, especially for diesel. Diesels would not start if you didn’t use one.

On a non-commercial sized truck, they’re basically a fashion statement. Older diesels and some very much older gasoline pickups really did have trouble warming up and staying warmed in extreme cold weather, but nothing made in the last 20 years should have any problem warming up in a timely manner and staying warmed up if the thermostat and the fan clutch are working.

With OTR trucks, the purpose is two fold. For one, the big diesels will have trouble staying warmed up when they’re idling overnight with the driver snoozing in the back. Secondly, if it’s cold enough out that full airflow through the radiator isn’t needed, covering over part or all of the radiator makes things a little more aerodynamic.

Engine block heaters are about starting. I believe this thread is about cold air while driving.

They’re becoming a lot less common for two reasons. Firstly, both gas and diesel engines are much better at starting in cold weather-- the limiting factor on modern cars is the battery, which a block heater doesn’t help with. Secondly, the other reason to have a block heater was that you’d get heat faster, but these days remote start switches are the more popular way to do that.

I’ve lived in the northeast my entire life, and have no idea what you’re talking about if the thing you describe is not a bra. So, no.

You don’t even live in Northeast Lite but in New Hampshire where it can get truly cold by any standard like Montana. If something worked to combat the cold, they should use it both places. I have lived in Massachusetts, New Hampshire, and Vermont and I don’t know what the OP is referring to either. It isn’t used commonly around here whatever it is.

Another factor is lighter oils. I started driving about the time 10W-30 became common. In 1992 I bought a Grand Am that called for 5W-30. In cold weather I notice a difference in how easy the engine turns over and they fire up sooner. This is true even with my ancient truck that still has a carb and points. This year I went a step farther with 0W-30 synthetic. Ford and Honda have gone to XW-20, I forget 0 or 5.

There are 2 factors. The warmer the engine and thinner the oil, the easier it turns over. The oil that counts is not what may be kept cozy by a crankcase heater, but the film in the bearing journals. A crankcase heater may help keep it warm too. Any sort of heater will make for faster warm ups.

Another question is when do I get some heat and also the windshield defrosted? Again, a crankcase heater or any other heat will help. Until the thermostat opens, all the water flows through the heater core. After the thermostat opens, blocking the air flow may force the heater core to do more of the work giving more heat to defrost the windshield and the driver. I am not sure how big of a factor it is in an water cooled engine, but a big blast of frigid air over the outside of the engine must have some effect.

The Cavalier I drive now is the first aluminum block I have had. I notice it throws heat faster than any of the cast iron monsters of the past.