To warm or not to warm...what says GRM

The pistons and sleeves warm up pretty quickly.  Bearings are a bit loose until warm, but the oil is thicker so they mostly cancel each other out.

When you start an EFI car in the cold, ever notice how it hangs up around 1000+ rpm for about 10 seconds?  That's the richest of the enrichment (and the IAC holding open to compensate).  After the idle settles back down in 10-15 seconds, oil is flowing everywhere, the pistons and sleeves have warmed up and are good to go.

I start, put on my seatbelt, turn on the radio, and put it in gear.  I drive a lot like a grandma anyway but I wouldn't say that WOT is very healthy until you see the temp gauge start to move.  The only time I let it warm up is if I'm feeling particularly wussy because it's particularly cold.  In those cases I sometimes start it up to de-ice and make the cabin warm so I'm not scraping windshields in 10 degrees cursing my choice to live in PA.  But that is strictly for my laziness.  I don't think its good for the car.

But I have also never seen major differences in all the engines I've torn down.  I know I've probably torn some down that were warmed up first and some that were abused when cold, but cylinder walls and bearings usually all look pretty predictable compared to what the odometer says.

I will say our Honda's windshield recently cracked from me turning the defrost on/warming it up when I guess it was too cold outside/too much ice/cold stuff on the window

has anyone ever seen a failure caused by either example? for years and years people have been warming their car up before driving, and others just get in and go. in both cases there have probably been little to no failures due to either starting method. i'd say do whatever you want. if you want to waste a little extra gas and let it get nice and warm for when you get in go for it. if you want to hop in and take off then do that. At this point i cant see any reason not to do either.

Curtis said:

The pistons and sleeves warm up pretty quickly.  Bearings are a bit loose until warm, but the oil is thicker so they mostly cancel each other out.

When you start an EFI car in the cold, ever notice how it hangs up around 1000+ rpm for about 10 seconds?  That's the richest of the enrichment (and the IAC holding open to compensate).  After the idle settles back down in 10-15 seconds, oil is flowing everywhere, the pistons and sleeves have warmed up and are good to go.

I start, put on my seatbelt, turn on the radio, and put it in gear.  I drive a lot like a grandma anyway but I wouldn't say that WOT is very healthy until you see the temp gauge start to move.  The only time I let it warm up is if I'm feeling particularly wussy because it's particularly cold.  In those cases I sometimes start it up to de-ice and make the cabin warm so I'm not scraping windshields in 10 degrees cursing my choice to live in PA.  But that is strictly for my laziness.  I don't think its good for the car.

But I have also never seen major differences in all the engines I've torn down.  I know I've probably torn some down that were warmed up first and some that were abused when cold, but cylinder walls and bearings usually all look pretty predictable compared to what the odometer says.

Yeah, thats to help fire off the cat.

I've owned  several straight six engines over the years.   All of them have been cold blooded, and liked to be warmed before heading off.  This is true regardless if it was my BMW, Toyota, Ford, or AMC.   For some reason they aren't happy until up to operating temps.

My TR6's transmission likes needs to warm up a bit before it shifts smoothly.

I always warm my older cars up a bit before driving---- they seem to appreciate it.  

z31maniac said:

Curtis said:

The pistons and sleeves warm up pretty quickly.  Bearings are a bit loose until warm, but the oil is thicker so they mostly cancel each other out.

When you start an EFI car in the cold, ever notice how it hangs up around 1000+ rpm for about 10 seconds?  That's the richest of the enrichment (and the IAC holding open to compensate).  After the idle settles back down in 10-15 seconds, oil is flowing everywhere, the pistons and sleeves have warmed up and are good to go.

I start, put on my seatbelt, turn on the radio, and put it in gear.  I drive a lot like a grandma anyway but I wouldn't say that WOT is very healthy until you see the temp gauge start to move.  The only time I let it warm up is if I'm feeling particularly wussy because it's particularly cold.  In those cases I sometimes start it up to de-ice and make the cabin warm so I'm not scraping windshields in 10 degrees cursing my choice to live in PA.  But that is strictly for my laziness.  I don't think its good for the car.

But I have also never seen major differences in all the engines I've torn down.  I know I've probably torn some down that were warmed up first and some that were abused when cold, but cylinder walls and bearings usually all look pretty predictable compared to what the odometer says.

Yeah, thats to help fire off the cat.

For modern cars, when lighting off the cat, the engine isn't running rich.  It generally runs just barely lean.

At 50F, that will be about the same, at 20F, it will be barely rich- just rich enough to run.  And at -20F it's more rich- but just enough to run smoothly.

There are emissions targets for 20F, 50, 70F, and 90F from a "cold start".  Above that, starts are included in other tests- up to a point, below that and the requirement is to have a running car.  But the higher idle speeds last a much longer time the colder the start temp is.

In reply to Papabishop :

Start drive gentle until properly warmed up. 

I let my disco idle for a moment or two before I begin to move. I can thankfully let it idle/move for a good minute before I have to apply any throttle. Same with work, If I am parked on the 5th floor, I idle/coast down to the ground and then give it some throttle when I pull out onto the street.

ice racing was cancelled due a week of 40s/50s in lower michigan. you tell me.

feels more like late march not jan/feb.

and yes my rotary cars have catalytic converters on it. AT LEAT IM TRYING! :p

im a very irritable person without ice racing and a proper winter.

I ran an article about this very question last year: Do I Need to Warm Up My Car? A Winter Primer

Pretty much with a modern car, it isn't necessary. I didn't get a flood of hate filled comments, so I'm in the "just drive it" camp.

I always figure this conversation needs to include what you consider a cold start.  Is it -35°F, 35° F, or 80°F?  

Makes a difference to me.

when its zero outside I can barely use my clutch pedal, it kind of snaps back and its hard to depress. It also it got so cold my dashboard cracked in the rx8. Last year my clutch pedal broke in the cold!

codrus said:

I've spent most of my driving life in parts of the country that never get cold enough to think about warming up before driving, but my impression is that the "warm it up before driving it" advice went out with carburetors.

This. If your oil is so thick that you have to let an engine warm up before use you're using the wrong oil. Oil analysis and engine wear are what I do for a living. 

codrus said:

Papabishop said:

In reply to dropstep :

Curious tho why more gas gets into the oil from idling. To me if that much gas is getting into the oil idleing then it would driving.. also is gas that much from diesel, because I've had trucks that have had plenty more hours idleing vs driving with no issues

When the engine is cold, the ECU has to run the mixture a lot richer or it'll stall.  This wets down the cylinder walls, seeps past the rings, and contaminates the oil.  It's not idling per se that's the problem, it's idling when the engine's cold.  By driving the car you're getting the revs up, putting more load on the motor, and warming it up faster, so it spends less time overall in a rich condition.

 

Diesels are direct injection, so I don't think they need the same kind of richening when cold.  Also, diesel fuel is a lot closer to motor oil than gasoline is, so even if you did contaminate the oil with fuel, it's not as big of a deal.

 

unfortunately this is completely incorrect. #2 Diesel fuel has a viscosity of around 2.1 cSt where a 40W (5-40, 15-40) is around 12-16cSt. So yes, fuel dilution is a serious issue in diesel and gasoline engines. 

Well guess I've been doing it wrong for years! My main defense was I've always let car warm up couple mins for 15+ years now, 3 of which that lasted over 200k and one up to 400k. Good to know tho, guess I can snooze in the am lil longer now in am 

In reply to z31maniac :

That is my warm up time too.

In the winter I let them warm up for a few minutes if I have time. (go outside, start, go back in and finish getting ready). It's nice to get into a relatively warm vehicle with a defrosted windshield when it's cold out.

When it's warm out it's start, seat belt, set up phone for music, drive. 

I'm in a warm area, I do the seatbelt usb plug 20 second warmup.  But even here I wont rev it out until 5-10 minutes into a drive.  Dash coolant temp shoots up way quicker than what your oil temp is.  That is what I figure into that 5-10 minute window.  In my head I see revs as worse than wide throttle positions.  But maybe I got it wrong..

People that purchase a new car every 3 years or so don't need to care about warming up the engine, but my 40 year old car with well over 200,000 miles gets warmed up nearly every time. I've owned the car since 1994 and it's still got the same engine in it as when I purchased it. Yeah, it is pretty tired, but still runs well enough. It usually only needs 3 to 5 minutes of warm up time, and it's not just for the engine, it's for the transmission as well.

I don't know that modern cars need to be warmed up, but I do suspect there is an concern when flogging a cold engine.  My RX-8 will limit engine performance if you attempt to give it above a certain number of revs (5k?) when not fully warmed up.  I've only discovered that when attempting to do a quick test run after replacing something.  eg. bedding brake pads.

Fedelity101 - RX-8 clutch pedals are designed to break.  I've broken 3.  Reinforcement bracket to the rescue.

Floating Doc said:

I learned long ago that it was more effective to start the engine, let it idle for 30 seconds to a minute, then shut it off to heat soak for at least a minute or two. 

Discovered it by accident. My first car was a 1960 Plymouth slant 6 with several hundred thousand miles on it. Started it up one sub-freezing morning, then remembered I had to go back in the house. Had to shut it off so I could unlock the front door. 

I did this somewhat by necessity on my '80 RX-7, which I stupidly drove in the winter.  (Bye bye Texas car)

I'd get about fifty yards down my street before the carb would ice and the engine would die.  Open hood, lift off air cleaner lid, spray windshield de-icer on the carb, close everything up.  Between the methanol in the de-icer, and the moderate amount of pre-heat applied to the carb after running for five-ten minutes (time enough to clean the overnight snow from the car, and then stall halfway up the street) it would be fine for the rest of the drive in to work.

And after I installed the MSD ignition, I could even let it idle on the choke by itself without having to blip the throttle all the time, without worrying about fouling the plugs and flooding out!

Snrub said:

I don't know that modern cars need to be warmed up, but I do suspect there is an concern when flogging a cold engine.  My RX-8 will limit engine performance if you attempt to give it above a certain number of revs (5k?) when not fully warmed up.  I've only discovered that when attempting to do a quick test run after replacing something.  eg. bedding brake pads.

Some BMWs have a variable redline depending on engine temp.

I know teh S60 R will make some unbearably bad engine noises under any kind of load with a cold engine.  Like rod knock times main bearing rumble kind of expensive noises.  Common wisdom is to not let the engine go into boost until the temp gauge is pointed straight up, and with the kind of sounds it makes, I follow it!  (What happens to bearing clearances on an all aluminum engine when everything is at 10F instead of 200F?)

The wait for the engine to come up to full temp is a very long one indeed!

I'm not bad about it though.  I had a customer who said his plugs kept fouling.  Turns out he would start it and idle it for, no exaggeration, about 45 minutes before driving off.  With plugs cold enough to survive 1000hp in a six cylinder engine.  Well, YEAH, you're going to foul plugs if you do that!

If I let the car warm up it is for me not the car. Or if it is snowing/sleeting out and I need the defroster to work.

thestig99 said:

In the winter I let them warm up for a few minutes if I have time. (go outside, start, go back in and finish getting ready). It's nice to get into a relatively warm vehicle with a defrosted windshield when it's cold out.

When it's warm out it's start, seat belt, set up phone for music, drive. 

The joys of having a garage. Even when it was 4-5° F out it still only gets down to around 40 in the garage. 

if I have frost on the windshield, I will start the car, set the defroster and scrape the windows.  Then drive of.  Takes a couple of minutes.  If no frost, no waiting. 

My wife will start her van and let it warm up on a cold morning if she has to take the little ones out, so they don't get put in a cold car.     

FYI in some locales, it is illegal to warm up the car.    Seems they get stolen quite often.