Winter Driving

November 9th, 2010 by Potato

I was just out getting the car ready for winter here, since it was a nice sunny day to do it. When getting the car ready for winter there are things for safety and things for fuel economy. Plus if there’s any regular maintenance you tend to do yourself, you may want to get that done and out of the way while you can still feel your fingers.

Tires: The biggest improvement you can make for winter safety is a set of 4 winter-rated tires, and I actually changed over back in October. I was a little early, as the time to change is when you can expect the temperature when you drive to be consistently below 15°C. Since I do most of my driving at night I felt comfortable changing over earlier, and got a good deal on the tires in the process (for the new car, I got a set of Gislaved Nordfrost 5s from Steelcase Tires in Markham). They engage in “supply and demand pricing” as they put it — they say that by November the cars are lined up around the block for winter tires and they won’t be offering deals anymore. If you need tires this winter, there may still be a few places with deals around (mostly the manufacturer’s mail-in-rebates), but I found last year that the deals didn’t come back when business slowed down towards the middle of winter, so you may be stuck paying retail.

It’s also important to check your pressures regularly, both for safety and good fuel economy. I like to run my tires a little hard, as it gives better fuel consumption and wear, at the cost of a rougher ride. The number on the door jamb is a compromise number set by the car manufacturer to balance ride, fuel consumption, tire life, and the suspension parts, and should be considered your minimum pressure. Your maximum pressure is given on the sidewall of the tires, and in-between those you can find a tire pressure that meets your preferred compromise. For the fall though, I recommend going a little higher than you normally would, because pressure falls as the temperature drops. It’s easier to over-inflate (still staying below the sidewall max) on a nice warm day than to have to go out on the cold days and top-up. The rule of thumb is that the pressure drops about 1 PSI for every 5°C drop in temperature. So if it goes from +5 to -20 over the next month, you could lose 5 PSI. Not really enough to be a danger on its own, but worth watching and reinflating.

The actual math is a proportionality P1*T2 = P2*T1 — note that you have to use the absolute (Kelvin) scale of temperature. So you see that for a higher-pressure tire, the drop in pressure will be larger than for a lower-pressure one. If, for example, I was to consider 40 PSI as normal for my tires (since I do like to run a little hard), then going from 277 K (5°C) to 252 K (-20°C) would be a drop of 4 PSI, pretty close to the quick rule-of-thumb result.

Windshield: It’s vitally important that you can see, which means you’ve got to have your snowbrush/ice scraper ready to go… which means you’ve got to have it in your car before you’re miles from home in the first snowstorm of the year and belatedly remember that you need it. Likewise you’re also going to need to clean your windshield as you drive, which is where wipers and fluid come in handy. Wiper blades generally need to be replaced at least once a year, and I find the fall a good time to do that (though I forgot this year so far). You’re also going to need washer fluid that won’t freeze on your windshield (or worse yet, in the lines), so if you’ve been using the pink bug stuff through the summer, time to start mixing in the antifreeze stuff.

This is also a good time to clean the windows, especially if you’re in the habit of using any kind of cleaning solution, which may freeze later on (these days I just clean my windows with a dry microfibre cloth).

Grill blocking: It’s a less common winter prep step, one geared just for fuel economy rather than safety. The concept is that your car has been designed for a very wide variety of environments: from the dead of winter, to rolling through death valley in full sunshine with the A/C blasting. So those openings at the front of the car are letting way too much airflow through when it’s freezing cold outside, making the radiator shed more heat than it needs to when it’s freezing cold outside, causing you to burn more fuel just to keep your engine’s temperature up. If you block off some of that airflow by insulating your engine compartment, you can improve warm-up time, save on fuel, and as an added bonus, help keep some of the salty slushy muck that gets kicked up off the road out of your engine bay.

For most cars, once the temperature is consistently below zero, you should be fine blocking well over half of the radiator, even under heavy loads (e.g., long hill climbs). Above zero, and you could risk overheating in some cases. If your car has a temperature gauge, watch it when temperatures start to rise; if it doesn’t, you may want to play it safe by not blocking except in the dead of winter, or get a Scanguage to monitor your temperatures.

The Prius (and I’m sure other hybrids) has a bit of a twist, as it has two radiators: one for the engine coolant, and one for the inverter. You do not want to block the radiator for the inverter: that’s a “cooler is better” component. For the Gen 3 (2010 and later), that means blocking the lower openings (the ones below the front license plate), but not the upper ones. I believe the Gen 2 is the opposite, but check that yourself to be sure.

As an aside, this step is even more important for a hybrid than a regular car, as a regular doesn’t have too much trouble staying up at temperature, even in the winter. A hybrid though will be shutting the engine off completely when it can, but for emissions control reasons it will have to keep the engine at operating temperature, a goal made all the harder by the cabin heater drawing off heat. So the benefit of shutting the engine off will be reduced in the winter as the car will cycle it on more just to keep temperatures up if you don’t block the radiator.

Battery: Due to the effect of the cold on your battery’s charge and the difficulty in turning over your engine, if your battery is going to go, the time it will give up the ghost will be in the middle of winter. If your battery is weak and due for replacement, you may want to replace it now. If you roll with one of those handy boosters (e.g., the Eliminator) in your trunk, then remember to charge it up!

Miscellaneous: I know that when it’s cold outside, I don’t want to spend any more time going over my car than I have to. I tend to get a little more neglectful of checking my fluids and tire pressures than I am in the warmer seasons, so this is a good time to check that all those other fluids are topped up. Also check on your first aid kit and flashlight, and replace stuff as needed. If you get into an accident, winter’s the time you’re going to need that little silvery mylar blanket, so make sure you’ve got one. If you don’t, ask anyone you know who runs marathons, they give them out like candy at those races. I like to wax my car in the spring, since the winter time seems to eat it all off. Waxing in the fall is also good because that water-repelling layer also helps repel snow and ice — I have a much easier time brushing the snow off the roof and hood at the beginning of winter while there’s sill some wax left there than I do by the end (and yes, you must brush the snow off the roof too!).

Have I missed any winter prep steps that you like to do?

2 Responses to “Winter Driving”

  1. Netbug Says:

    I like to just huddle in my basement and not go out until April of the next year. Saves on all this prep.

  2. jonathan Says:

    what about the flux capacitor, any tips on winterizing that?