What's current best practice for warming up a vehicle?

[ecotourist]

In over 40 years driving manual transmission, I can't recall any of mine that didn't have a clutch interlock and it had to be pushed down.

For sure:
'65 Comet [I drove this vehicle 30 miles when the clutch linkage failed. It started in first gear and I could rev match through the higher gears.]
'63 Chevy II
I think:
'78 Fiesta
'81 Celica
Maybe the '00 Solara, the '00 BMW and the '07 Accord. I can't say for sure as I now depress the clutch automatically when I start.

 

[NA4U]

Yep I do the same I wait for the preheat to kick in and RPMs to drop then I drive easy for a few.

But I have noticed a lot of people in my area especially where I used to walk my dog.
I would take her on a two mile walk daily at lunch time, And often would see the same people sitting in their cars from start to finish of my walk with their engines idling.

Talk about carbon buildup and premature maintenance intervals. I guess they have no clue.

 

[Sequoiasoon]

I live in the South East ( Carolina ) so I have cool mornings, but only a few COLD mornings.
On a Cold morning I have ALWAYS walked outside and started my car truck ( long before remote start ) walk back inside and let thing warm up a good 5 min but those days are seldom ( a few times a year I guess ).

My daughter sent Ring camera video from neighbor in CT of girl across the street. She did that. 1 minute later car pulled up, 2 of the areas finest residents hopped out of theirs and into hers. It was never recovered.

 

[Hohn]

I personally don't ever need to do extended warmups because I use climate- and application-appropriate oils and my engines warm pretty quickly.

Heck, on my K20C Accord, the coolant temp rose from a cold ambient of 45F to 95F before I left the parking lot at work on the way home. It was 125F when I got to the gas station 4 blocks away.

With such rapid warmups while driving, it seems pointless to let the car sit and idle a lot. Especially as a TGDI with a known propensity for oil dilution by fuel.

 

[fdcg27]

Start it and go, driving gently for the first five or six miles especially if the weather is really cold.
If the windows need to be cleared of snow and ice, I'll brush off the driver's side to avoid getting snow in the car and then get in and start it and then finish clearing off the snow.
I rarely use remote start, maybe half a dozen times in the seven years I've had the car.
Incidentally, if you leave the car idling unattended because you figure out that you need to go back in the house to grab glasses or wallet, the car cannot be driven even though running without the fob, so any would-be thief would be out of luck.

 

[SOUNDMAN5000]

My daughter sent Ring camera video from neighbor in CT of girl across the street. She did that. 1 minute later car pulled up, 2 of the areas finest residents hopped out of theirs and into hers. It was never recovered.

WoW, If one must worry now about an Amazon package I guess one must a car too... That white mist vaping out the tail pipe on a cold morning could be a calling card for a not so nice person.
I'm not sure but I think some States / areas may have a law about leaving a car running and not being in the car?

 

[GW.]

We usually get 2-3 weeks of this every winter, sometimes colder.

 

[f355spider]

Just got back from Fairbanks, AK last week...it was -7 to -10 most mornings (dash thermometer). I started the rental Altima and whatever it took to clean off the frost or dusting of snow and drove off...between one to two minutes. I noticed the past few years, very few cars or trucks in the rental fleets in Alaska have block heaters...this one didn't.

I asked a few locals what they did...most said the same...start and go within a minute or two. A couple had remote start and will give it a good 5 minutes or more of ideling to warm the interior. Most seem more concerned with warming the interior than warming the engine.

In more normal weather...no colder than teens, I have had two seasoned mechanics tell me it was best to drive off within a minute or two, as ideling, while it may warm the engine a bit, was doing nothing for the transmission or differential. Driving off and being gentle the first few miles was a better way to warm up the car than sitting an ideling in their opinion.

 

[Hohn]

Extended cold idling is bad because of the dynamics of fuel vaporization.


From a vaporization perspective, you'd want the hottest intake air temp that won't autoignite the fuel, and you'd want it at high velocity for effective tumble or swirl (depending on port design). In either case, the goal is rapid vaporization.

But obviously, really hot intake air will tend to knock like crazy, so we can't just have superior vaporization. It also means the air has very low density, so the engine will lose power even as it gains efficiency (this was the idea behind smokey yunick's old "hot vapor" engine concept).

When you start a cold engine-- especially a cold GDI or TGDI engine, the vaporization is poor because 1) the air temperature is very low and 2) there's very little time for the vaporization to occur before combustion.

So a cold engine spews raw fuel out of the exhaust. This is why we have cats and (especially) pre-cats. This is why your cold started engine gets such awful mileage for the first trip. This is why you can tell just by smell if the car in front of you on a winter day is warmed up or was just started.

That raw fuel is washing down your cylinders. It's contaminating the oil film in your ring pack , especially at the critical top land.

The cold idle scenario increase the fraction of total fuel burned under sub-optimal conditions. This accelerates oil degradation and aggravates the tendency towards deposits.

 

[CleanSump]

My daughter sent Ring camera video from neighbor in CT of girl across the street. She did that. 1 minute later car pulled up, 2 of the areas finest residents hopped out of theirs and into hers. It was never recovered.

Coworker here had it happen to her. They either were very lucky driving around looking for someone leaving their car to warm at 6 am or they had canvassed the area and were prepared for her to be their target.

 

[goblin]

And the joys of it are not only that, but in some states it will be much easier pleading joyriding if one drives away in a car left idling, unlocked, key in ignition, as opposed to forcing locks and hotwiring.
Plus it's an infraction in several states to leave a car unattended with the key in the ignition.

In some places in Europe leaving the car unlocked key in ignition is considered inciting theft, there's some penalty for that.
Same when a car thief abandons a stolen car - if they leave the key (supposing they had one) in the ignition, or leave the hotwire easier to jumpstart again - the penalty is heavier. Because you're inciting the next guy to go rinse repeat.

 

[skyactiv]

The only time I warm it up is if say I'm at work and I need to clear snow or ice off it. I don't care if we have a cold snap and it's -2 out. If the windows are clear and I've been at work my 10 hour shift, I start and go but drive easy on a cold engine.

 

[Sumboodie]

Warming up a car by idling always seems to be an act of futility to me. It takes a very long time to warm up an engine at idle. And from reports I have read, the rings don't seal as well at idle on a cold engine, resulting in excess bypass.

In cold weather an engine needs to be warmed up no more than 30 seconds to a minute before driving. I keep it under 3000 rpm until the coolant temperature gauge starts indicating that the temperature is rising, then drive normally. The exception is when there is frost on the windshield. Then I start the car, turn the defrost on, and start scraping the windshield. When the windows are clear, so it is safe to drive, then I go.

In summer, I idle the engine about 20 seconds before going.

When it's cold, it's going to take longer than 30 seconds for all cylinders to even be firing and oil to flow, nevermind trying to drive!

I'll weigh in on this topic as a North Dakota native and engine guy.

The "best" practice is to start the engine. Do you have oil pressure? There is a rough ratio of time to build oil pressure (from cranking) to time where oil has reached all the rest of the engine. It's around 5:1 on the upper end. So if it takes one second to have oil pressure in the main oil rifles, you'll have oil at the top end and everything else within 5 seconds. This is true even of the massive 95L V16 QSK95 Cummins makes, which has oil pressure at the mains in under 2 seconds even on a cold (near freezing) start .

Which means that after 5 seconds or so, the engine is not receiving any more oil or any better lubrication. There's no advantage to further idling in terms of engine wear reduction because you're already in full elastohydrodynamic lubrication (let's call it EHDL, please).

IN bitter cold temps with marginally suitable oils, it might take 4 or 5 seconds to have oil pressure at the main rifles. Which means it could take as much as 25 second or so to get oil to the top end and all the rest of the engine.


So, regardless of ambient temperatures, idling more than 30 seconds is not beneficial if you chose an oil that is remotely appropriate for your local climate.

Engines make more heat at higher rpm and with some load on them. That's pretty obvious. It's also obvious that your engine will warm up faster then if it has some load on it (i.e. driving) instead of idling.

Elevated RPM in a cold engine is your friend, within reason. Keeping it around 2000-2500rpm assures good oil pump output, good coolant flow (and heat distribution) and it also reduces wear at the top ring reversal.

So what is "ideal" is cold start, idle no more than 30 seconds, then take off driving gently (mild throttle) but allowing the engine to rev to keep engine torque low.

Now, if you idle longer to scrape window or whatever, you're not really hurting the engine by much of anything measurable. It will shorten oil life and that's about it.

Use a really good high viscosity index oil with a nice dose of Moly, a pour point at least 20 degrees lower than your coldest start, and a cranking viscosity under 6000cP at your worst case start. Then get on with life.

Most of my stuff isn't even hitting great on all cylinders in 30 seconds, never mind ready to move when it's cold. Easily a good 20-30 mins to get some heat into the engine and it making a semblance of power.
High idle is fine. But that's ~1000-1200 rpm. Std idle around 600-700rpm. 2500 is getting up there on revs for alot of engines.

Of course "warming up" at 30* is much different than at -30*, or colder.

 

[Sumboodie]

In over 40 years driving manual transmission, I can't recall any of mine that didn't have a clutch interlock and it had to be pushed down.

I've never had one on anything I've owned, though probably a few had them at the factory.
83 Chevy C30, 05 WRX, 05 Elise, 81 and 83 Mercedes 406, 05 Jetta, 91 Mustang, 81 S2574 International, 91 Mack RD688, 81 Ford F900, etc.

 

[Sequoiasoon]

Nothing like missing it is NOT in neutral and cranking it forward or backward into something.

By me they won't install remote starters in manual transmission for that reason. Liability.

 

[Lubener]

No warm up time for me. I drive away after approx. half minute after statring.

 

[69GTX]

I think I've read here that getting to an oil temp of 165-175 deg F is when you are past the point of warmup/cold corrosion occurring.
So getting there as quick as possible is the goal. I leave my car in 3rd gear and shoot for 1600-2000 rpm (35-45 mph) until it's reasonably warmed up in 2-3 miles.....coolant temp 150F-200F. And that's about the point I'd be getting on the highway.

 

[Marcozi]

I let the engine revs drop to normal and then drive very gently. I lug the engine until the oil temperature gauge “needle” has started to move. “Lug”? The car has a manual transmission so after the car is moving I’ll shift into 3rd gear instead of 2nd gear.

 

[Hohn]

When it's cold, it's going to take longer than 30 seconds for all cylinders to even be firing and oil to flow, nevermind trying to drive!

Most of my stuff isn't even hitting great on all cylinders in 30 seconds, never mind ready to move when it's cold. Easily a good 20-30 mins to get some heat into the engine and it making a semblance of power.
High idle is fine. But that's ~1000-1200 rpm. Std idle around 600-700rpm. 2500 is getting up there on revs for alot of engines.

Of course "warming up" at 30* is much different than at -30*, or colder.

The fact that it's not running smoothly is not indication that oil hasn't been flowing. A HEUI injector engine like a Powerstroke or CAT is quite well known to really hate cold oil and not start very well. But that doesn't mean the low pressure oil pump hasn't done its job or that the engine isn't well lubricated. It just means the injectors aren't happy. HEUI injectors needs much more oil flow (and lower viscosity) than the rest of the engine.

LIkewise for gasoline engines. Oil as thick as ~6000cP can lubricate effectively (that's why that was the rough upper viscosity cutoff chosen for the "w" ratings). And it is flowing (slowly) to the top of the engine. And it will flow and lubricate effectively even if the pistons are so cold they don't support gasoline vaporization.

IN summary: ineffective combustion is not evidence of ineffective lubrication. They are different functions with their own temperature sensitivity curves.

 

[KrisZ]

Can we reach 10 pages of bitog cold start routines?

The world needs to hear people’s routines, how you turn on the radio, put on the seat belt, what the RPM is, how all of the warning lights turn off, and for Chrysler and VW owners, which ones stay on.

And we need to do this every fall.

Come on people, we can do this.