They Say Don't Let Your Car Warm Up Before Driving In Cold Weather?

After starting my cars all last week at over -20°F I always let the autostart warm up my cars for the full 18 minutes they come programed with but they say don't let your car idle to warm up, just get in and drive. Now I read this:

"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."

For many reasons, I just can't believe any of this can be true. Besides the obvious reason that it sucks to drive a car that's -10°F inside the passenger compartment with frosted over windows, I would think that it would be a smart idea to let the transmission whether automatic or manual have a chance to warm up the fluids?

And yes, I always plug in my engine block heaters at 10°F and lower temperatures.

I have always heard the argument not to waste fuel but this is the first time about washing down the cylinder walls with gasoline with an over rich air/fuel mixture.

Yahoo.com: Country Living: No, You Probably Don't Need to Warm Up Your Car Before Driving It

As well as modern cooling systems are designed to promote quick warm up, I also have a hard time agreeing with this. As you also mentioned there is the safety factor of having defrost functioning.

That was taught to me back in my apprenticeship days.

To this day, I do not let my vehicles warm up - Once it starts, I'm moving.  It will warm up faster in use.  I don't do a big smokey hazer down mainstreet until the engine is up to temp though, I drive it nice.

One thing to consider is that you really don't see the colossal ring-ridge wear on the cylinders of fuel-injected engines like we did on carb'd engines back in the day. I attribute that to less excessive fuel washing oil away.

Having said that, my 6.0L LQ4 fires up cold at 8:1 (AFR gauge on the dash) and is idling at 14.7 easily within a minute.

Actually working the engine would probably cook the moisture out of the oil quicker and more thoroughly, though.

It's been -35c all last week.

I warm my truck up. The transmission shifts like garbage when it's that cold. The EPS is stiff and awful too.

Anything with oil in it works much worse when it's that cold. Seals can leak or blow out.

The pcm handles warmup enrichment just fine.

Sorry Scotty Kilmer, there's more going on than just running the engine.

It's worse for the engine to rearend a parked car because you couldn't see where you were going because the windshield iced over when you started moving because you didn't have working defrost yet.

If I can, I let mine warm up.  Admittedly, it's less about the engine health and more about the meatbags in the cabin.

I think on modern vehicles it ultimately doesn't matter much. Modern engine control systems are very advanced but can't work magic, everything still takes longer to warm up at idle than under load. I assume letting it sit is marginally worse but not enough to really feel bad about it. I care more about my comfort than the car's comfort 😂. The only thing that's really bad is starting a fully cold vehicle and immediately running it hard. Other than that, don't put too much thought into it.

I typically let me car warm up while I fasten my seat belt, adjust the radio, check the mirrors, and generally get settled, and then I go.  I'll drive gently for the first couple miles until the temp gauge starts to move up.  On subzero days I will give it a minute or two longer to warm up before I pull out of the driveway.

Remember that besides the engine, the transmission and rear end need to get warmed up too, and that won't happen unless the car is moving.

In reply to stuart in mn :

Isn't a transmission spinning while in park or neutral, automatic or manual? At least some of it?

In reply to VolvoHeretic :

Yes it is, but most of the heat in an automatic comes from the torque converter, and it only makes heat based on the difference between input and output speeds under load. (Specifically, how much more torque the converter is putting out vs. what is going in)

This makes driving off from cold VERY amusing with mine, after putting the high stall speed converter in it.  When the fluid is very cold, it will will not go into lockup, to heat the fluid faster.  I live two blocks from an Interstate on ramp.  The trans will upshift through to 6th gear but the engine speed will stay at 3000rpm the whole time like a CVT.  Go to accelerate and the revs swing up a lot, let off the throttle and the engine drops to near idle.  Then the fluid gets to 40F or whatever the threshold is and the TCC engages and suddenly it's a rock solid 1900rpm.

I note that there's been a trend in cars for 10-20 years to use a water-oil heat exchanger mounted to the transmission, instead of a radiator mounted one.  The cooler in the radiator only sees hot coolant after the thermostat opens up.  The trans mounted one can get its coolant feed from a similar place as the heater core, to warm up the trans fluid faster.  (Also, no more trans lines, which has several benefits of its own)

Fuel injection has definitely helped with the cold and idle mixture condition that would leave excess fuel to wash the cylinders. Manufacturers are also more aware of air flow (swirl and tumble) and how it can help keep fuel suspended for emissions and economy.

So some of the reasons for not warming up are gone, but the other part is lubrication of components that aren't lubricated by pressurized oil. Warm oil drips down to the pan overnight and leaves lifters, rockers, chains, guides, etc with less oil at startup. The oil isn't slung around the same way at idle as it is at higher rpm, and I would assume it's even less when the oil is cold and thick.

The example that comes to mind is the 5.7 Hemi and the lifter failures. Depending on who you listen to, part of the problem is the cam being higher up in the block making it harder for oil thrown from the crank to reach the cam and lifters at idle. Higher rpm's sling oil further and keep the rollers lubricated. 

I typically start the Mini, then put it in neutral with my foot off the clutch while I put on my seat belt, connect my phone, and get some music playing. Then I'll take it easy on it with rpms staying between 2-3k until I start to get decent heat. I reverse the process when getting close to home and then in the driveway before shutting down to let the turbo temp drop before shutting it down. 

The Kia gets less consideration and will be started and allowed to idle longer while getting ready to go, and frequently files for extended period of time at the rink before and after hockey games/practices. 

I  let mine warm up in single digits and below. I  live approx. 3 miles from work. If I don't let it warm up a bit, I will not have any real heat by the time I get there. It will just be starting to warm up when I turn into the parking lot. 

In reply to No Time :

A lot of the reduced wear that we see isn't so much from the EFI as it is that, due to concerns over NVH and long term emissions, the automakers aren't inclined to make engine blocks out of "ferrous peanut butter" anymore.

Some older engines, like small block Chevys, were made with very, very soft iron!  No wonder they practically needed 4 bolt mains.

Meanwhile, I had an iron block VWAG engine that lived a long time running full rich due to various issues (it was only happy with the WOT switch ziptied shut, it would run poorly if you tried to run closed loop).  At nearly 400k miles the bores showed no significant wear and there was no cylinder ridge that you could feel once you wiped the carbon off.  Better materials caused that, definitely not better mixture control!

In reply to Pete. (l33t FS) :

I'm not saying EFI was the only reason, but helped address one of the contributing factors to cylinder wear at idle. 

Each engine has its own set of design decisions made and they contribute to longevity, or lack of it, under different conditions. 

Living in VT this winter there are plenty of cold mornings on my way to work. In my Gladiator I pull up the Oil Temp and watch it as I start driving. While driving I try to keep the revs between 1500-2000 until the oil is up to at least 75°. The crazy thing is that with the 0w-30 my oil pressure comes down to ~30psi at idle pretty quick. The transmission shifts pretty well even on sub zero mornings. The XJ runs 10w-30 so I try and baby it a bit more on the coldest days. It takes longer to warm up but I'm getting warm air out the vents by the end of my 4 mile drive to work. The biggest difference is shifting a cold transmission. The XJ runs thick gear lube(and it's got 350k on it) and it doesn't 'snic' into 2nd as nice as the JT.

The OP says he's running a block heater, so I woud say absolutely no warmup is needed, just jump in and go.......

In reply to MiniDave :

Block heaters don't heat up oil, just a small part of the block, or maybe some of the coolant. 

This is an acute issue if you have an engine that sends all of its oil through hoses to a cooler.  Chevy still does this.

I do NOT let a rotary over 3000ish RPM until the oil is warm enough that idle oil pressure drops from 60-80psi to at least 40.  Hot pressure is 20-25.  I don't want to blow out a hose or cooler.

Iirc my Dodge diesel's manual says not to let it idle to warm up. Start and drive. That thing has a big enough cooling system and thermal mass that it's not going to generate heat for a while anyhow, especially not at idle. Bundle up :)

Being able to pre-heat/cool the interior is the best thing about an EV. 

As for washing the walls with fuel, that's a concern with poorly tuned aftermarket ECUs - although I don't know if it's based on actual experience or just theory. 

One thing about fuel mixture- even though the combusted amount may show it as stoich, it's probably still injecting more fuel than warm stoich when the engine is cold- it takes a while for the system to fully warm up and not "lose" fuel.  And yes, a large amount of lost fuel ends up in the oil.   That's why you really want to drive a cycle where the engine oil gets up to as close to 200F as you can- to drive out as much of the gas you can.

As far as I know, pretty much all OEM's do unassisted starts down to -20F, where you can just drive away.

But the key about driving away as quick as you can and just letting it idle- it warms it up faster, less fuel in the oil, and the oil warms up faster.

If I had a frosty window, I would start it, scrape, and drive away.  But I also rarely have to do that- garage FTW, and for the last few working years, we had a parking structure- so almost no frost.  

I always let my car warm up when it drops below 65 degrees.  #Floridalife

Seriously, when I did live in the cold I would start the car and clear any frost off.  Then get back in and just drive.

And then as soon as you start rolling, the moisture laden air condenses on the windshield, and instantly freezes... 

What is the BMW that doesn't even show the top 2-3k of the tach until it reaches operating temp?

Until the temp gauge stops saying "low" I keep it under 3k

I'll remote start my Maverick and let it run. But that's to defrost the windows and defrost myself before driving.

Otherwise, I start driving the second the cold start high idle drops.

Pete. (l33t FS) said:

And then as soon as you start rolling, the moisture laden air condenses on the windshield, and instantly freezes... 

I've never had this problem living in cold snowy areas, both Lake Tahoe and Southern Vermont.

In reply to buzzboy :

That's definitely a thing i've experienced. I had a couple that would frost the inside of the windshield.