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

So with recent freezing weather we've had here in south Texas, a coworker of mine told me I was stupid for letting my car warm up. This coming from person who doesn't even change their own oil,  Where as I've been wrenchin for 15+ years I reply back  your stupid. So he pulls up reports on his phone from "engineers" saying letting car warm up is waste of time and causes damage to engine because of gas getting into the oil.... which I found humorous considering I've warmed up every car I've owned regardless of temp outside which I've had several cars with over 200k on them. Anywho what does hive think bout this? Find it hard to believe letting car warm up will cause damage to it.

I just don't see why. I've always gotten in immediately and driven conservatively until it's fully warm. I'll keep the revs down and not go WOT. The car warms up much quicker under light load than it does idleing.

I understand the engine getting warmer quicker by driving it. I'm not concerned with getting heater to work. But I feel letting oil/rings getting lil warmed up before driving is best.

Direct injected cars recomend no warm up and judging by the amount of gas in the oil during winter months i can see why. Some load on the engine will bring it up to temp faster and help the rings seal.

On my old beater i always let it warm up a good 5-10 minutes when its below freezing.

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.

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

Unless your cars are still carbureted, letting the engine 'warm up' for more than a few seconds does nothing but waste time and gas. So congrats on that. While "causes damage" may be a bit overstated, considering how long many engines can last regardless of abuse or neglect, there is apparently still a negative net effect. Not positive, or even neutral.

Don't be too quick to discount what "Engineers" have to say, just because of some inconclusive anecdotal evidence and it not being the way things once were. Having admittedly limited knowledge of a subject (like not even changing their own oil) can often leave people more open minded to accepting new information, as it's generally less challenging to their ego.

TLDR: Your coworker appears to be right on all accounts.

Down to 20F or so I just get in and drive (gently).  Below that and the vehicles seem to be happier with a few minutes to get their fluids flowing somewhat before driving.

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.

High fuel pressure sprayed directly into the cylinder with cold rings. Driving puts a load on the motor and warms it up faster. Warm rings seal alot better.

Let’s not forget oil viscosity has changed. The average, archaic v8 of yore ran on mud, whereas modern stuff runs on water (0w20). The thinner oil lubes better when cold. Drive it like ya stoled it. 

I drive a carbed B2200, so I let her warm up for 5 min or so when it's cold out. 

Remote start in sub-freezing weather. Only enough time to scrape ice and clear snow, usually less than five minutes. 

And the seats are warming too. 

If you can see out the windshield, drive off.

Most automakers do engine tests where they freeze the engine and fluids down to some really low temp, then start it and as soon as oil pressure is stable, WOT on the dyno it goes.  Then it gets re-cooled and the cycle is run over again, for many many hours.  You aren't necessarily going to hurt the engine.  You just risk hurting the CAR if the windshield ices over as soon as you start to move.

I'm a humid person, so I need a lot of defrost.  It's easier to just drive with the windows down, but this isn't always possible since cold weather usually means the windows are frozen shut.

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.

 

Right- it's not idling that's the problem, it's the very slow warm up of the engine that's the problem.  First- it's more time for fuel to get into the oil, and second it's cold oil that takes longer to purge the fuel out of the oil.  

As long as the oil moves, it's doing it's job.  Which also is a good time to remind people to not just put thicker oil in for the sake of it- put in the recommended oil since it has been tested to well below -20F.  

Personally, I don't wait for a car to warm up any before I drive- and that includes my 205k Miata that I drove every day, including when it was -20 outside.  Get in, start, drive away.  Heck, even my Alfa says to do that- it's only restriction was to keep the load and revs to a reasonable amount.

BTW, the issue for carbs is that they have pretty crappy cold temp compensation.  So you are far more likely to have a cold carbed engine stall or stumble than one with fuel injection.

DI is kind of a different ball of wax.

Knurled. said:

If you can see out the windshield, drive off.

 

Most automakers do engine tests where they freeze the engine and fluids down to some really low temp, then start it and as soon as oil pressure is stable, WOT on the dyno it goes.  Then it gets re-cooled and the cycle is run over again, for many many hours.  You aren't necessarily going to hurt the engine.  You just risk hurting the CAR if the windshield ices over as soon as you start to move.

 

I'm a humid person, so I need a lot of defrost.  It's easier to just drive with the windows down, but this isn't always possible since cold weather usually means the windows are frozen shut.

You saved me a bunch of time by posting almost exactly what I was going to write.

I would have added something about turning seals inside out on automatic transmission when the trans oil is more like Vaseline than atf.

For my modern EFI cars, "warm-up" consists of how long it takes to get my seat belt on.  With my TDI (and other diesels), I will plug in the block or coolant heater when I could, which helps it start easier (and in the case of the TDI, warm up a lot faster), but even if I couldn't I would just take it easy on the go pedal until the temp gauge starts to move.  I'll usually leave the heater completely off until the gauge shows about half way to full temp.

My old British cars are a different story.  None of them particularly "like" starting in cold temps. The '64 Mini with twin SU's down-right hated starting in cold weather (40 deg F or less).  I've found Zenith-Strombergs to be slightly more tolerant of the cold than SU's.   Either way, none of the three generally like any attempt at moving until I can at least get the choke mostly off.   When you get used to the instant "start and go" of modern cars, getting into a vintage car takes some adjustment in remembering how things happened at a bit slower pace 30+ years ago.

An interesting thing I read recently which questioned why so many LBC intake manifolds have a passage for coolant to run under the air-way post-carb as well as why they generally pull air directly from the engine bay rather than being ducted from ahead of the radiator.  Simply put: warmer air holds the fuel vapor in suspension better than cold air, so cold air intakes can be less effective on carburetted engines than one might think and definitely less than for EFI engines.  

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. 

It would run rough when it was cold, and when I came back out to start it up it ran like it was warmed up even though the temperature gauge hadn't moved yet. 

I don't really do this anymore much at all, all of my fleet are fuel injected. It also doesn't get that cold here in Florida very often. The rare exception is my extremely high mileage 88 Chevy truck since the lifters sometimes will make some noise when it's below 32. 

If its under 20f out, and the car has fully cooled outside, I will warm it up a bit first, or, if I have to immediately jump on the highway. If it is warmer, I just drive easy until the water and oil temp come up. Beware that on many cars, oil temp comes up more slowly, and you may not be 'warmed up' for high revs and heavy pulls just yet. The 'heat soak' method seems to work well on carbed cars. I read in the 1967 vw beetle service manual, to just drive the blessed thing to warm it up, so thats been my stance.

Most mfg are now solidly in the just drive it camp. Living in the rockies, I do let my car idle about 30sec, and installed an oil/water cooler, that has the bonus effect of equalizing water and oil temps and warming me up a bit faster. 

In reply to Nugi :

Up here, just south of the tundra, the temp has been -30 several times and only warming into the -20s during sunny days. Cars/trucks sit outside all day, modern cars have no problem starting and with thin oil recommendations, don't have cold oil circulation problems. Start them, wait 30-60 seconds and drive away. Take it easy until warm air is coming out of heater ducts.  Change oil on extreme temperature recommendations because of previously mentioned gasoline dilution. 

20 degrees is like a heat wave up here and 40 with sun is almost shorts weather.

I try to just stay out of boost until it's warmed up. 

Keep the revs/load low and/or stay out of boost. 

Both the BRZ and now the 135i warm up time was:

1. Get in car start.

2. Open garage door (while putting on seatbelt).

3. Back out of garage and drive.

Although with the 135i it's hard to stay out of boost in the morning since it spools so quickly, so I have to drive very gingerly!

KyAllroad (Jeremy) said:

Down to 20F or so I just get in and drive (gently).  Below that and the vehicles seem to be happier with a few minutes to get their fluids flowing somewhat before driving.

This is what I do.

I had the exact same thing happen to me. A non-car enthusiast told me I was wrong for warming up my 185k Miata for ten minutes. I was all "I know cars, you're an idiot." 

Turned out that I was wrong. Unless it's got a carb, don't warm it up.

It was a good reminder to practice the Zen idea of "beginner's mind." 

Start car, give it a ten-mississippi for mechanical sympathy, drive away gingerly.