The myth about warming up your car on a cold day

Globe & Mail ^ | February 25, 2015 | PETER CHENEY

[rickmichaels]

The Stegosaurus disappeared more than 100 million years ago, doomed by its tiny brain and a changing world. Then we come to the carburetor, a crude fuel-mixing device that once ruled the automotive universe.

Today, the carburetor is largely extinct, kicked aside by the modern fuel-injection system. Yet millions of drivers still seem to be stuck in the Jurassic Period. I thought of this recently when I watched a man spend 10 minutes warming up a fuel-injected Toyota that could have been driven seconds after it was started.

Few processes are as poorly understood as the cold-weather start. Back in the days of carburetion, a car couldn’t be driven until it was warmed up. Today, warming-up is a counterproductive exercise that wastes fuel, harms the environment and damages your car. Let’s have a look at the science, history and flawed folklore behind the automotive warm-up:

[Bulwyf]

I warm my truck off before I go, and then I let it idle all day... usually minimum 12 hours.

I’m just doing my part to ensure we all don’t freeze to death.

[Chickensoup]

I have a 2013 diesel and my son says I need to warm it when it is a cold start and not in the garage.

[Chickensoup]

what about turbodeisels?

[Bob434]

[[That’s why I got in the habit of using synthetic motor oil during the winter months when I lived in Canada. Its viscosity isn’t affected by the cold the way traditional motor oil is.]]

Yes, but it doesn’t taste as good

[Kenny Bunk]

Back in the early foreign car days, some European auto manufacturers took a long time to learn not to use a choke and a throttle on their export models. Americans customers had forgotten how to operate these handy controls, which had been common on American cars in the 20's and 30's. But the Euros did include such handy instructions as these:

For extreme cold weather start, follow this E-Z 10-step process:

(1) Turn on headlights for 30 seconds to warm battery
(2)Fully depress clutch and hold
(3)Depress accelerator 1 time and release
(4)Hold accelerator down less than half way. Hold steady, do not pump.
(5)Pull choke out, rotate to lock.
(6)Operate starter in short bursts
(7) When engine catches, slowly push in choke gradually as RPM increases, while gradually pulling out throttle
(8) With throttle, set RPM a 1500-1800
(9)With gear selector in neutral, slowly release clutch.
(10)Push choke all the way in and idle in neutral at 2000RPM, reducing RPM with throttle to hold 2000 RPM for 5 minutes, or until satisfactory operating temperature is indicated.

Repeat as needed, or until battery fails, or buy American with an automatic choke. Or use a block heater. Or curse helplessly. Eventually the automatic choke reached Europe.

[Rockpile]

I will bet that this Toronto writer has a heated multi-car garage.

[PieterCasparzen]

Yes, I agree.

This is of course mostly for the lurkers out there...

Engine and Transmission are a bunch of metal parts - different metals - that fit together and - and a number of the parts either move or need to from an oil seal between them.

Things have to fit right.

Metals expand as temperature increases, shrink as temperature decreases.

Trouble is, different kinds of metal and metal alloys do this expansion and contraction at different rates.

http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

The engine will therefore be designed with a normal operating temperature.

A great example of operating temperature and metal expansion is the freaky case of the SR-71 and it’s fuel leakage on the ground until wings got up to temperature in flight.

The temperature of the engine is not the same all over; some parts are hottest, others less, still others are in a place where heat is dissipated quickly and they are relatively cool.

Car engines have bearings in them as well, which are precisely fitted and also have specified operating temperatures.

Operating the engine and transmission outside of their normal operating temperature ranges will cause excessive wear on parts that lubricating oil can not fully compensate for.

Also, as someone else noted, even at normal temperatures, operating a vehicle for extended periods near or beyond its normal operating limits or patterns (”beating” the car, etc.) will cause excessive wear.

I saw a guy drive his chevy impala (no slouch of a car back then) never use overdrive, but always use the top gear - a few years later his transmission needed to be rebuilt.

When two metal parts move against each other as they do in engines and transmissions, very small, tiny, pieces of metal are removed from one or the other or both parts. This is why the oild becomes darker in color; you’re seeing a cloud of minute metal shavings suspended in the oil. Of course, the oil between two moving parts will also contain the “shavings” - and make additional metal removal happen at an even faster rate than when the oil is brand new and clean. Viscosity breakdown is only part of the story of old oil; dirty oil may be the exact right viscosity specified, but will cause excessive wear.

Pressures between moving parts increase at different times and directions of movement in heavy throttle settings when under load. Thus, “pedal to the metal” causes excessive wear on engine and transmission parts, as does towing or carrying heavy loads.

[trebb]

Exactly - get the interior habitable before driving it - my wife also turns on her heated seat. The problem is that many newer cars run lean enough when cold that they don’t warm up so good when idling.

[octex]

When I start a vehicle and it idles at about 1500 RPMs, I let it run until the idle drops below 1000 RPMs before driving it. In the summer this can take 15-20 seconds, while on very cold winter days this can take 4-5 minutes.
*************************************
I know I’m late to this thread, so most posters have moved on.

I have an ‘01 Impala with 3800 V6 engine and it idles near 700 RPM. If doing 60-70 on freeway it’s only around 1200 RPM. ...........What kind of a beast car do you have that idles at 1500 RPM???

I bought new ‘68 and ‘72 VW Beetles and was told each time that no warmup was required in cold weather. That turned out to be true, but I can’t figure out why.

[Alberta's Child]

The two vehicles I’m referring to here are an SUV and a full-sized pickup truck. The truck idles at about 1500 RPM at start-up, then drops down below 1000 shortly after that. Once it’s been on the road for a while and I come to a stop, its normal idle is around 600-700 RPM.

[Malsua]

what about turbodeisels?

It's still a turbo, they're usually just bigger on diesel engines. Besides diesels need to warm up so they will run properly.

[Chickensoup]

How warm? 2 minutes? Five minutes?

[Malsua]

How warm? 2 minutes? Five minutes?

Depends...How cold and did you use a block heater? It also depends on your engine, depends on the personality of your vehicle. I only ever dealt with bigger truck(350, 450, etc, not Semi)

30 degrees...3 minutes.

0 degrees, no block heater(if it even starts) I'd say 7-10 minutes.

0 Degrees, block heater, 5-7 minutes.

You want the engine oil 100+ degrees before you start loading the turbo.

Your mileage will be crap on your diesel before it gets up to temperature. Some of the latest Turbo Diesels probably just do fine with a minute or two warm up. Some of the old ornery trucks I used to deal with probably needed to idle 24x7 :)

[logi_cal869]

There's a term applied to which this article refers:

'Puffing'.

It is illegal in some jurisdictions.

Sadly, there will be more.

[Kenny Bunk]

Alaska Rules: Leave the diesel running from October to May

[Covenantor]

You had an automatic choke?

I wasn’t allowed to drive until I mastered the mystery and art of using the manual choke.

Geezer am I.

[Responsibility2nd]

Yeah. I learned to drive in 1973. As I think about it - the oldest car I ever drove was a 59 Chevy Bel Aire.

I don’t remember that car having a choke (automatic or manual) at all.

[Liberty Valance]

[going hot]

The motor is made of many different metal parts, each having their own perfect size when at operating temperature, designed to have the correct clearances between moving parts.

When the motor is cold, the clearances are not at specification because the parts have not sufficiently expanded to their operating size, ie, fully warmed up.

Driving away while the motor is below ideal operating temp wears the parts down at a tremendously accelerated level.

[Tenacious 1]

I warm my truck off before I go, and then I let it idle all day... usually minimum 12 hours.

That's a waste of gasoline. It's cheaper to just burn your garbage in the back yard along with recycleable plastics. It stinks for a while, but it's efficient and saves space in the trash been. It also saves your local government some money, all while helping to heat our global climate.

Over the summer, my neighbors complained about the black smoke and the smell. But now that it's REALLY cold out, they understand my logic. On Saturday afternoons, my neighborhood looks like the burning oil fields in Iraq circa 1991. LOL!