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| © Ezra Dyer The long-held notion that you should let your car idle in the cold is only true for carbureted engines. |
In the thick of winter, the common wisdom is that when you are
gearing up to take your truck out in the cold and snow, you should step
outside, start up your engine, and let it idle to warm up. But contrary
to popular belief, this does not prolong the life of your engine; in
fact, it decreases it by stripping oil away from the engine's cylinders
and pistons.
In a nutshell, an internal combustion engine
works by using pistons to compress a mixture of air and vaporized fuel
within a cylinder. The compressed mixture is then ignited to create a
combustion event—a little controlled explosion that powers the engine.
When your engine is cold, the gasoline is less likely to evaporate
and create the correct ratio of air and vaporized fuel for combustion.
Engines with electronic fuel injection have sensors that compensate for
the cold by pumping more gasoline into the mixture. The engine continues
to run rich in this way until it heats up to about 40 degrees
Fahrenheit.
"That's a problem because you're actually putting
extra fuel into the combustion chamber to make it burn and some of it
can get onto the cylinder walls," Stephen Ciatti, a mechanical engineer
who specializes in combustion engines at the Argonne National Laboratory, told Business Insider.
"Gasoline is an outstanding solvent and it can actually wash oil off
the walls if you run it in those cold idle conditions for an extended
period of time."
The life of components like piston rings and
cylinder liners can be significantly reduced by gasoline washing away
the lubricating oil, not to mention the extra fuel that is used while
the engine runs rich. Driving your car is the fastest way to warm the
engine up to 40 degrees so it switches back to a normal fuel to air
ratio. Even though warm air generated by the heater core will flow into
the cabin after a few minutes, idling does surprisingly little to warm
the actual engine.
The best thing to do is start the car, take a
minute to knock the ice off your windows, and get going. The obvious
caveat here is that if it's below freezing, you need to make sure your
defroster is working before you go tearing out of your driveway. Don't
be the person peering through a porthole in your ice-covered windshield.
Some cars, like certain Land Rovers, expedite this process with
electric heating elements in the windshield.
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| © Ezra Dyer Warm it up, Kris! (But just enough to get the defroster going so you’re not peering though an ice-porthole as you drive.) |
Also, hopping into your car and gunning it straightaway will put
unnecessary strain on your engine. It takes 5 to 15 minutes for your
engine to warm up while driving, so take it nice and easy for the first
part of your drive. Performance cars often enforce that process with a
graduated rev limiter—you don't get full RPM until the engine is up to
temperature.
Warming up your car before driving is a leftover
practice from a time when carbureted engines dominated the roads.
Carburetors mix gasoline and air to make vaporized fuel to run an
engine, but they don't have sensors that tweak the amount of gasoline
when it's cold out—they use a mechanical system called a "choke" to
temporarily restrict the air intake and run a richer mixture.
This
is a crude way to adjust the air-fuel ratio, and anyone with a
carbureted engine can attest that it's hard to drive under load when the
carb is choked. It's easy to stray too rich on the mixture and foul
your spark plugs. As a result, you do need to let older cars warm up
before driving or they will stall out. But carbureted engines were on
their way out by the late 1980s.
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| © Ezra Dyer OK, you’re probably going to need to warm this one up and get that defrsoter going. We told you there were exceptions. |
We asked Volvo, which conducts cold-weather testing in the Arctic,
whether their new cars need any sort of warmup, and the answer was an
ever-so-slightly qualified no. According to Volvo, "It’s best to just
give the engine a few seconds to build oil pressure before driving
normally. Good oil quality and condition are crucial for protecting the
engine in cold start conditions."
The Engine Block Heater
If only there were a way to get your car's fluids up to
temperature—and thus get the heater and defroster going—before actually
starting your car. Well, there is: an engine block heater. Block heaters
use an electrical element to preheat your engine's fluids so it's ready
to go (and easier to start) when the temperature drops, thus explaining
the three-prong plug poking out of the grille of your neighbor's
definitely-not-hybrid F250. They're a common option on trucks, with
Chevy charging only $100 for a block heater on a new Colorado (gas or
diesel), but they can also be retrofitted to just about any vehicle.
Aftermarket block heaters
are also inexpensive, and can be well worth the money when you consider
the reduced wear and tear (and generally more pleasant mornings) they
deliver.
So that's it. Unless you're rolling in a 1970s
Chevelle—which we assume isn't your daily driver—bundle up, scrape off
your car, and get it moving.
