Is Driving a Really Cold Car Bad?
The idea you should warm up your car before driving in really cold weather is so ubiquitous, it almost seems like an urban legend. In fact, until the mid-1980s, it was beneficial. Today’s gas engines are so advanced, the practice is all but unnecessary; diesel engines have warming plugs and anti-freezing external plug-ins that the operator must know how and when to use.
Other People Are Reading
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Old Wives Tales and Facts
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Some people insist it is necessary to allow a cold engine to warm up until the choke switches off without RPMs dipping below its normal idle speed. Others believe that once the temperature gauge starts to rise above its rest position, the car can be driven. Vehicles certainly should not be driven until the defroster function has heated up enough to clear the windows; visibility is good. Further, a warm driver is likely to be safer than a driver bundled up in restrictive clothing, hunched against a miserable environment.
The Science
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Power steering and braking fluids and transmission and lubrication oils are all more turgid at lower temperatures, and seals are less malleable, so warming up is not going to hurt. Those fluids also are susceptible to the law of gravity like everything else; they settle to the lowest points available to them overnight, and in really cold weather, they can take a while to become fully viscous again and be delivered to their points of use. Excess friction is bad. Karl Brauer, editor-in-chief at Edmunds, tells BankRate.com, “Revving is especially bad for your engine if you do it right after you start the car when the engine is cold and all the oil is still down in the oil pan.” That said, warming up has a tradeoff in wasted gas.
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The Cut-Off Era
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Older cars benefited more from warming up because they used less sophisticated materials and technology than do today’s vehicles. Modern oils and engine management systems make the practice almost obsolete. As a rule of thumb, a carbureted car will benefit from a warming-up period in moderately cold temperatures -- anything approaching freezing, or 32 degrees F -- while a fuel-injected car probably will not. Most manufacturers changed over aspiration systems in the mid-1980s. Enthusiasts who drive older cars, even with new oil and replaced seal kits, should allow some warm-up time, because the metals used in manufacturing the older engines are rather more brittle and less forgiving than modern materials.
Exceptions to the Rule
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In certain circumstances, for instance if you live a hundred yards from a steep freeway on-ramp that you have to gun the car to climb -- all the while accelerating to freeway speed -- waiting a little while is a good idea in any age car.
Extremes of Cold
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“Really cold” is a subjective term. In sub-Arctic conditions, where temperatures can plunge to below minus 40 degrees, warming up is certainly beneficial for vehicles of any age. Pistons and cylinder heads generate much more heat than does the crank, so the top end could heat up markedly faster than the bottom if an engine was revved high and hard immediately upon starting. The worst case scenario would be a cracked engine block from the massively disparate expansion rates. Although this is very unlikely, warming the engine up for a few minutes is cheap insurance.
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