‘Warming Up’ Your Engine In Cold Weather Is Actually Not Good For Most Vehicles
It's been deeply engrained in our minds to let your vehicle warm up before driving it during subzero weather like we're currently experiencing. While that was once good advice, truth is you don't need to anymore, at least from an mechanical perspective. It also isn't great for your engine.
Before getting into the mechanical thought behind this statement, I readily admit that a major motivation to warm your car up is to warm the interior of your car for your comfort. While that is a legitimate reason to do so, just know that experts warn that this isn't the best idea for your engine.
Modern vehicle engines work differently than older engines. Older vehicle engines (like several decades older) rely on carburetors that do need to be warm to function at peak efficiency. Newer vehicles now use computers and other technology that don't need to be warmed up to function. A report done by the U.S. government actually states that most vehicle manufacturers say idling your vehicle is undesirable if unnecessary. Obviously we all have to stop at red lights and whatnot, but letting your car simply idle to warm up isn't ideal.
The report also states that catalytic converters warm up much faster when vehicles are being driven, rather than when idling. This means that a cold, idling vehicle is using fuel less efficiently and spewing more pollution into the air than one that is being driven cold.
Popular Mechanics (via Business Insider) also explains that allowing a car to run at an idle in cold weather can actually cause harm to the engine over time. When it is cold outside, gasoline doesn't evaporate as rapidly. The computer that controls the fuel injections system compensates by injecting more fuel into the combustion chamber to help with combustion until the engine warms up to about 40 degrees, where normal combustion can occur and the engine doesn't need as much fuel.
Because it takes longer for an engine to warm up idling than it does while driving, this exposes the cylinders and pistons to more gasoline which can cause problems. Gasoline acts as a solvent, and can strip oil from the cylinder walls and pistons, which can lead to more friction and wear to a crucial part of the engine. Less lubricant and more wear is not a guaranteed recipe for immediate disaster, but it is definitely not good for the overall life of these components.
It is worth noting that other vital fluids in your car (engine oil, transmission fluid, power steering fluid, etc.) are also cold, so "letting 'er rip" at 55 mph right after starting your car at -20 probably isn't the absolute best idea either. Experts advise you "take it easy" until your engine and the fluids warm up a little before pushing your vehicle too much. They say this is the quickest, most fuel efficient, and safest way to warm up your vehicle. In extreme cold, allowing your vehicle to warm up for a minute or two before taking off may be necessary just to make sure all fluid lines are passing fluid. That is, assuming you don't drive a vintage vehicle a 1970's pickup truck that still has a carburetor-based engine and legitimately needs to warm up first.
Along with the fact it doesn't do much for the vehicle (beside giving you a warm place to jump into), the City of Duluth and many other cities actually have ordinances in place where you could be ticketed for your vehicle left idling, especially unaccompanied. These ordinances are in place not only as a measure of cutting down on emissions, but also to prevent car thefts, which are pretty commonplace during extreme cold with plenty of vehicles running and waiting for thieves.
Save yourself the possible ticket, engine wear, and the extra gas. Yes, you'll have to sit in a cold car for a few minutes, but you're (hopefully) wearing a coat, hat, and gloves anyway for your walk to your vehicle.