Idle time during cold weather

[gto78]

yeah that's true. I convince myself of that each morning as I leave my house late for work...lol. I try to drive it easy until it's fully warmed up, which in my case means I pull out of my driveway, go one block, pull onto the main road, drive 45mph for 3 miles, then make a right turn onto the turnpike and gun it pulling into 80 mph traffic. My warm up period is a consistent 45mph drive with no stops for 3 miles. My oil still gets slightly dirty after a year but holds up great. If my oil was turning black after a few months I'd be worried about blowby, but it's been fine.

[8307c4]

I don't see any harm in a 5-10 or 10-20 second warm up either, but speaking from an FE standpoint longer isn't doing any real favors. It is best with sticks, we can get going in idle, I like to think of the first 30-60 seconds as crucial warm-up time (almost no gas, if any) then the first 1-2 minutes very little gas (just enough to keep from looking the fool).

And so on, gradually a little more for the first 4-5 minutes until I'm up to normal driving, this can vary a little depending how long it takes the car to warm up.

In the case of carb'ed cars one does have to 'twitch' the throttle to get the choke to fall out of its geared hold, this I understand, more so before putting it in gear or its rpm's are too high... And on some very old cars, certainly there can be the kind that quite simply stall if we get going at all too soon, you do what you have to do in order to keep the nonsense at bay.

But no, absolutely never a burst of power, or gunning it right off.

There's more:
I've learned to never gun it at all, this in itself helps, just one full throttle or even heavy throttle acceleration per one tank of fuel hurts mpg by a few 0.1's... So if you normally get 20.4 mpg then one nice heavy acceleration likely just dropped that to 20.3 or 20.2 for that whole tank of fuel, doing it more doesn't help.

I'd say heavy-footed acceleration can account for a 10-20 percent difference vs. keeping light-footed, which, I still don't see the logic in pulse-and-glide (thou maybe hybrids are different, and possibly electric motors do benefit from 100% vs. less, but gas?).

[Snax]

Well there is a difference between pulse and gliding vs. gunning it and gliding. Yes, sticking ones foot in it for the acceleration part does dump in more fuel, but using 1/2 to 3/4 throttle typically does not pump in such a large amount of fuel. Slower is typically better, but there is no need to feather it in either. It also depends on how quickly one applies throttle. (Throttle pumping is the culprit, wherein fuel is literally dumped in before airflow and sensors catch up to what is about to happen, typically resulting in a rich condition for more responsiveness.)

[Jernnifer]

Any expert will tell you that you should only warm your car up in winter for at the most 30 seconds, anything else wastes gas.
Jennifer

[VetteOwner]

now anyone who knows anything about cars will tell you to let it warm up longer depending on the temp as parts love to wear out fast when there's little or no oil on them :P

those "experts" probably get a new car every 2 years anyways so they dont care about us who keep them for 20 30 years!

[theholycow]

Heheheh, a user's first post ever is one bumping a year-old thread.

Anyway, I don't buy into long warm-ups for modern engines. The only people saying they're necessary anymore are individual consumers. The manufacturers, who have to honor longer warranties than ever (including Chrysler's lifetime powertrain warranty), say wait 30 seconds to let the oil circulate then drive off (but don't flog it until it's warmed up). It makes sense to me, and 180,000 miles into my 2002 GMC I haven't had any problems from that practice.

[GasSavers_GasUser]

Nice old thread. Depends on which vehicle I am using (one that slept in the garage all night where it doesn't get that cold even if it is 20 below) or the one in the driveway.

If it's the one in the garage, I just start it and it idles for a minute or less and easy does it for a mile or so.

If it's the one in the driveway I start it and usually let it run for a couple of minutes to 3 or 4 minutes max only if it is real bitter cold out (especially 0 or below). Just because it is so bitter cold. If not so cold I don't let it run more than a minute or less.

Number one priority for me is engine/drivetrain wear and tear. I don't care about fuel economy at all during warm-up. I care about major costly components (engine/tranny/drivetrain, etc) that cost thousands of dollars. Driving it easy for the first mile or so helps the entire drivetrain warm up together as opposed to letting it idle 15 minutes and having a semi-warm motor and stone cold tranny/diffs etc.

When it is bitter cold out, it takes 10 miles or so for the drivetrain to get to operating temps. Anything less than that is severe use on the drivetrain. When my heater starts blowing real hot and the engine temp gauge is at 195 degrees then I know it's all properly warmed up.

Just my opinion.

[Snax]

Regarding oil warm up and circulation:

IF you are using the proper oil, it is most certainly circulating throughout every nook and cranny with effectiveness within milliseconds. And IF you are using the proper oil, it does not need to warm up to do that.


That said, I think there is an argument to be made for varied rates of thermal expansion having an impact on wear and longevity - but most modern motors already have provisions for that built into the clearances - the most important of which is ring gap. I.e., too little and the rings can expand faster than the bore, bind, and cause additional wear.

So the question becomes how well the motor was actually spec'd out for assembly. The last motor I built for instance was built on the loose side and it showed at startup with audible piston slap for the first 5 seconds or so. Fortunately modern massed produced engines don't have that issue and the engineers have it pretty well figured out that millions of drivers will pay no attention to warm up, so they've built that into the specs.

But like everything else on this board, YMMV!

[VetteOwner]

milliseconds? i think not but yes its near a second or 2, especially the uppers cuz it does drain down.

i know if its too cold the engine may be warm and runnign smooth but the manual tranny will be cold and i cant shift it. or the truck with hits hydrolic clutch the fluid willbe so cold it will feel like your stepping thru cold butter...

[R.I.D.E.]

When we prelubed engines we rebuilt (absolutely no oil in any of the galleries pump or filter), we used a drill and a shaft to drive the oil pump with the cylinder head off. It took about 6 seconds for oil to shoot out of the passageway to the head up to the 12 foot ceiling.

Once that was done the oil would shoot up after less than ten revolutions of the drill, because all the galleries were already full and the filter was full also. The Nissan filters had a rubber disc that acted as a check valve to prevent oil from draining out of the filter.

Bottom line, when you start the engine cold, as long as your filter doesn't drain into the crankcase, you have oil pressure in less than a half second of run time. My 37 Ford with a cranking speed of 100 RPM would get 50 pounds of oil pressure in a few seconds cranking, after not running for a month, with no oil filter whatsoever.

My car stays in my garage. I start the engine put it in gear and go. Now if your car is covered with ice then you have a different situation.

regards
gary