Idle time during cold weather
 

Has anyone experimented with idle time during cold weather (without a block heater?)

I usually start the car, wait about 10-15 seconds and drive away. My logic being that the engine will warm up faster if I put load on it, and it would wear less than letting a cold engien idling and warm up way slower...but I never thought about which uses more fuel.

Maybe the engine would use less fuel if I let it warm up at idle for 1-2 minute, and use less fuel if I only drive if after???

mmhh...

BTW I'd love a block heater but its not worth the price now, this is my car's last winter, I want a beater civic or tercel hehe :)

what i always hear is that from an FE perspective it's best to drive off slowly right away... take it easy on the engine. after all when it's really cold it's not just the engine that needs to be warmed up but allso all the lubrication in the bearings and the transmission... the heat to do this will come from friction when the car is moving... wich is not good news for FE but there's no way around it.

a grillblock is a cheap way to air your warmup slightly and if it's cold the risks of overheating ar minimal.

so my advice it to avoide idle whenever possible

I got a large sheet of plastic aat home, I think I'm going to cover half my my radiator or something.

I drive mine as soon as the rpm's settle, which takes a few seconds at most.
Just take it real easy for the first few miles, if the driveway is flat I usually don't even give it gas for the first 20-30 seconds but in gear it is and I'm off.

yea you wanan keep the rpm's as low as possible, the thicker oil has to be pushed thru the tiny oil jets and most liekly there isnt enough. thats why most engine wear is start up because there is no oil lube.

When its really cold, I like to crank the engine until the oil light goes off- usually 8-9 seconds. That way at least the main and rod bearings are getting oil. Then I pump the gas pedal once and it fires right up. Of course this pre-lube starting technique only works on a car with a carb.

A fuel injected car usually fires up immediately- I guess the guys with the injector cut off switch could use my cold start tactic.

Unless I need the defroster running, I drive off immediately, paying no special attention to rpm beyond normal hypermiling by trying to keep them low.

How cold is it where you are?

We've been very cold, and that's a judgement call now isn't it, and I'm looking for a couple minutes of warm up time. But I really need that.

Movement will generate load, but it will also generate air movement across the block, etc.

I would start looking at the scangauge engine temp and like suggested just take off without any gas. You auto guys have it tough however and at least park so you don't have to back up to start off. Have friends that park nose in and have to back up a steep driveway and turn around when the engine is racing - talk about working the power steering and banging the tranny around in an automatic!! OUCH!

I give it 10-20 seconds for oil to circulate and un-congeal from the cold then go easy on it. darn thing warms quick but barely stays warm anyway why bother trying to warm it up.

yea thats what i do depends on how long and sluggish it sounds to crank over

tommorows goign to be a long one gonna be 0*F:(


lol when its rreally cold and i try to drive the chevette the engien will start with one pump of the gas and about 5 seconds of cranking but the choke doesnt instatly close so you have to manualyl keep the gas down for a few seconds then release the clutch in neutral and it usually dies. fire it back up and its good lol. tranny can get so thick i cant shift outa first, or if i do i cant go into 2nd:p

My commute is only 6 miles, so if the temperature is below about 20F in the morning, I will let the car warm up in the garage (door halfway open). Other than that, I just put the jacket on and go.

I'm a penny pincher and can't seem to let myself buy an electric block heater.

My commute is short enough that the engine is still warming up by the end of it. My best mileage consistently comes the same days the final temperature is the lowest. Less engine runtime = better mileage, even when that running time is with a cold engine.

I don't think congealing, outside of real extremes, is a concern with modern oils.
I was doing some wood cutting in cold weather, high 40s to low 50s, and the chain saw bar oil was flowing like chilled honey. So I used some used motor oil. To the eye, it appeared to flow like new oil on a warm day. It also may have been synthetic.

That said, I let the ranger start rolling nearly as soon as it starts up. I have heard that letting a Prius warm up nets better averages. It may go through its pre-functionary warm up cycle quicker without the load of moving.

My car has 174,000 miles on it, and 10w30 oil, so it really doesn't need warm-up, I just drive real nice and easy for the first few miles.

Oil needing to warm up is one major factor, another factor is the "blowby" that goes past your piston rings. Our engines are designed to run at a certain temperature, and when they're cold they have different clearances/tolerances. The cold pistons are not perfectly round, they're slightly oval shaped. (this is because there's a lot more aluminum mass in the areas where the piston pin slides through it) As the pistons get up to operating temperature they will expand into their normal size/shape. But until they warm up there will be a lot more wasted gases that blow past the rings and make the oil turn black.

Another point is that the piston rings are like springs, sprung outward towards the cylinder walls. When the piston is cold the rings are extended further out of the piston than they normally are. This makes it possible for carbon and coke deposits to get behind the piston rings inside the grooves, which causes the rings to jam up tighter to the cylinder walls over time. This is a major cause of wear and it also causes ring sticking, and sometimes broken rings, and ring lands.

Basically letting the car idle for as long as possible is the cleanest way to drive, but not always practical. Driving while cold will warm it up faster, partially because the blowby gases are heating the oil directly...

While I don't disagree with you've just pointed out gto, I don't believe the effects of this are as significant as they may seem. I'm not suggesting that one should immediate go full throttle on a cold motor, but having torn apart and built a motor, I've seen the effects of my own significant abuse.

In a nutshell, what I am suggesting is that the temperature of the pistons and rings themselves adjust fairly quickly, as opposed to the block and other rotating assemblies. Being in direct contact with combustion and thermally isolated from the rest of the block, they are likely typically close to full operating temperature within a minute. (Piston slap from a cold loosely built motor disappears literally within a few seconds because of this.)

That still leaves open other issues of expansion and tolerances that change, but as I said, I believe it's less of an issue than it might seem.

expansion and tolerances DO change. bearing tolerances are in the thousanths of an inch and thermal expansion of iron, steel, and aluminum across 200 degrees (0f on startup, 200+ while running) is several thousanths. intake valves for example are given as much as a hundredth of an inch of clearance to account for thermal expansion, exhaust valves even more.

oil thickness is a concern for me because when it's 0 outside, the cressida's engine will turn over about 500rpm and slowly rise to 1500 in about 30 seconds. once it reaches 1500, if I let the clutch out in neutral, the oil viscosity on the gears drops the engine revs to 900. that's part of the reason I got the truck and don't drive the cressida right now when it's cold. the truck barely notices even in 0f

On the aircraft I maintain, I see the same customers weekly and have known and maintained over half of my customers planes for almost 10 years. I've paid attention to the customers habits (some are always in a hurry and others are perfectionists). I've had to do top cylinder overhauls on almost every one of my customer's airplanes. With that said, it's always the same exact situation- the customers who don't wait for their engine to warm up, they just start it and haul *** for the runway before reaching operating temp (which should take about 10 minutes) always have problems with oil consumption, broken rings, overhauls that are needed 200 hours prematurely, burned up camshafts, blown turbos etc.

Our other customers who are more laid back, they start up, sit back and read through checklists, double check the flight plans, make a few last phone calls etc. Then they head for the runway, then eventually take off. These customers always have extremely clean oil changes, they run their engines hundreds of hours past the recommended overhaul, and in the long run save tons of money on maintenance.

It's more than just waiting for a thorough warm up, it's also the driving style and amount of abuse. But the bottom line is that the engine is designed to work/produce power at a specific operating temperature, and when we exceed that range then we will end up with more trouble in the long run.

But consider that the very first thing that motor is going to be asked to do shortly after startup for those in a rush: A full throttle burn.

So obviously that does illustrate your point on the wear, but those of us who simply drive away without gunning the motor aren't placing much more stress on it than if we simply let them warm up fully by idling.

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.

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?).

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.)

Warming up your car
 

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

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!

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

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.

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.

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! ;)

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...

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

So, yes, "milliseconds" vetteowner, milliseconds. ;)

As Gary has pointed out, there are checkvalves to prevent drainback, and in systems lacking that, the positive displacement design of the oil pump prevents drainback. This essentially assures that oil is ready and waiting in the oil galleys of the head and crank journals to move as soon as pressure is developed by the pump. Full oil pressure is usually reached within just a few rotations of the engine actually firing.

The bottom line is that the delay in flow and pressure from not running to running is so miniscule as to be something you really don't have the opportunity to impact.

I.e., worry more about having the proper weight oil rather than driving on a cold motor. Motors are built to handle thermal shifts, but not oil that can't get to where it is needed.

I sure am glad my Synlube bonds to the metal surfaces and provides lubrication even when the lube is not circulating.

right on! a good quality 0W30 changed at recommended intervals is about as simple as it gets.

I was always told to let it warm up for a few minutes because it can cause cracked heads if not. during high school my mom would go out and start my car like 5 minutes before I was ready to go. I never understood it, but whatever, she payed the gas bills then.

But now I get in, turn it on, wait for the RPMs to settle, then wait a few more seconds. Usually this takes 30-40 seconds in 10* weather. and obviously scrape windows if need be during this time. Then I just drive off slowly, trying to apply as little gas as possible (automatic). My tranny doesn't like to shift from 3rd to 4th very well if it's really cold, so I may get up to 2800 RPMs before it'll shift (have to get on a 65mph highway after about 4 minutes of residential). it usually takes until this point to reach operating temperature, or about 5 minutes. when warm it usually shifts at around 23-2500 RPMs with the way I accelerate.

I try to balance the line between idling too long and using fuel and allowing the engine to be ready. It may not be totally right, but it makes me feel better.