Idle time during cold weather

[VetteOwner]

Originally Posted by kamesama980

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

[GasSavers_DaX]

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.

[palemelanesian]

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.

[trollbait]

Originally Posted by kamesama980

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.

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.

[slurp812]

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.

[gto78]

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...

[Snax]

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.

[kamesama980]

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

[gto78]

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.

[Snax]

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.