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Here's the Real Reason You Should Never Warm Up Your Car

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#1
Johnny D

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http://www.roadandtr...rm-up-your-car/

 

It takes longer, wastes fuel, and actually increases the wear and tear on your engine.

1470235861-warm-up-car.gif

 

On cold winter mornings, some folks will fire up their cars and leave them running for 10, 20, maybe even 30 minutes, thinking they're reducing wear and tear by letting their cars warm up gently. But Jason from Engineering Explained is here to explain why that's a bad idea for your car.

 

(This post was originally published on August 3, 2016 and has been republished because it's getting damn cold outside for much of the country. - Ed.)

The conventional wisdom that you should idle your car up to operating temperature comes from the days of carburetors, which needed several minutes of idling to get to an operating temperature where they'd run smoothly. With fuel-injected engines, the ECU can adjust itself to idle perfectly even in sub-zero weather. And as Jason explains, idling an engine doesn't really build up much heat at all, compared to driving it.

 

Jason goes through the details of what happens in a cold engine, and points out the hidden damage of letting your car idle for a long time on a cold day: Engine oil dilution. It turns out, while you might have thought that letting your car slowly warm up was reducing wear and tear, all that idling time leads to raw gasoline seeping into the oil, breaking down the oil's lubrication properties and increasing the wear.

 

So what should you do? Start it up, make sure all your windows are clear of ice/snow/fog, and just drive the thing! The engine will warm up faster, and therefore you'll get nice warm heat coming out of the vents sooner, which is what you want anyway.

 

Watch for yourself and let a real engineer explain why you should stop warming up your car.

 


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#2
Erik Hardy

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I'm not buying this shit one bit. My diesel truck is thoroughly pissed off below 0C. I feel like I can hear the pistons rocking a bit the first couple revs after its colder than -20C, but not sure exactly what the noise is. The thing that I don't see being addressed is oil viscosity v. temperature and coefficient of thermal expansion.

 

We are already at -20C in Michigan. Its more of chunky grease than liquid oil at this temperature. They should try the cute oil in wine glass with -20C to -40C oil and watch it not move.

 

Very non linear graph:

 

tdtgcetc.jpg

 

Then add aluminum pistons in cast iron cylinder sleeves, with aluminum having twice the thermal expansion of iron.

At cold climates the piston to bore clearance is horrible, giving the pistons the opportunity to rock in the cylinder :(

 

 Not saying you can't go run it but man it doesn't seem worth it. 


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#3
Johnny D

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They should try the cute oil in wine glass with -20C to -40C oil and watch it not move.

 

Why don't you. :)

 

If you have the time.

J~


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#4
Erik Hardy

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lol I just might!


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#5
Erik Hardy

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I couldn't fill up the racecar trans/diff oil last winter (unheated garage) because the oil wouldn't go down the transfer tube. Had to wait until spring :)


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#6
Johnny D

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Isn't the "W" in 10W for winter ?  How winterish is it ??

 

VISCOSITY

Most oils on the shelves today are "Multigrades", which simply means that the oil falls into 2 viscosity grades (i.e. 10w-40 etc)

Multigrades were first developed some 50 years ago to avoid the old routine of using a thinner oil in winter and a thicker oil in summer.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100°C. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100°C etc. Your handbook will specify whether a 30, 40 or 50 etc is required.

 

Did you use a 10W oil ?

 

No clue on diesel truck.

 

Just sayin

J~


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#7
Ron Alan

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He said diff/tranny Johnny if you are referring to the post about waiting until spring with your 10w question? 90w below 0 might move pretty slow!


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#8
Johnny D

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He said diff/tranny Johnny if you are referring to the post about waiting until spring with your 10w question? 90w below 0 might move pretty slow!

 

Were all over the place, apples and oranges, and if's and but's were candy and nuts..

 

So the article posted is talking about a car (corvette) on gas, what weight? idk, is there a corvette owner in the house?

I thought this would be related to starting our race cars.

 

Then posted about "My diesel truck is thoroughly pissed off below 0C"  ,different correct ?

 

DIESEL
CD - Introduced 1955 - international standard for turbo diesel engine oils for many years, uses single cylinder test engine only
CE - Introduced 1984 - improved control of oil consumption, oil thickening, piston deposits and wear, uses additional multi cylinder test engines
CF4 - Introduced 1990 - further improvements in control of oil consumption and piston deposits, uses low emission test engine
CF - Introduced 1994 - modernised version of CD, reverts to single cylinder low emission test engine. Intended for certain indirect injection engines
CF2 - Introduced 1994 - defines effective control of cylinder deposits and ring face scuffing, intended for 2 stroke diesel engines
CG4 - Introduced 1994 - development of CF4 giving improved control of piston deposits, wear, oxidation stability and soot entrainment. Uses low sulphur diesel fuel in engine tests
CH4 - Introduced 1998 - development of CG4, giving further improvements in control of soot related wear and piston deposits, uses more comprehensive engine test program to include low and high sulphur fuels
CI4 Introduced 2002 - developed to meet 2004 emission standards, may be used where EGR ( exhaust gas recirculation ) systems are fitted and with fuel containing up to 0.5 % sulphur. May be used where API CD, CE, CF4, CG4 and CH4 oils are specified.

 

Then he jumps to his tranny. So is that related to starting your car in the cold??

Maybe, can you wear out your tranny ?

 

Then I post an example which happens to be 10W-40 oil

 

I'd be interested in learning everything. Does a 80W-90 really thicken up, it's got the magic "W" ?  And how low does it really go, don't cha know, up north a.

 

This was what I was looking at and posting from

http://www.driverste....co.uk/oils.htm

J~


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#9
JRHille

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Bobistheoilguy.com

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#10
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Here be a Yooper oil viscosity test. The first test is at 1*C or 34*F. Nut eben cold fer dem yoopers.


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#11
Erik Hardy

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lol sorry for confusion. Yes Johnny, 80W oil will thicken up to the point where it completely stops flowing in a tube basically below 0C. Put a jar of honey in your fridge, then see how well it flows. Motor oil does the same thing, on a exponential scale with temperature.

 

The yooper test is only at 1C. At -20C, which happens all the time here, the oil will be 4 times thicker! Basically a milkshake :(

 

Following up Hille's link:

https://bobistheoilg.../motor-oil-101/

 

So your oil is milkshake, your pistons have shrunk a couple thousandths in comparison to the cylinder liners so they can physically rock in the cylinder....Its a terrible combo. When we have another cold day I might take a video of some oil in a wine glass...its pretty terrifying at these temperatures.


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#12
davew

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In my 40 years in the auto industry, w has always stood for weight. If it stood for winter, why would 120w-150 drag racing gear oil have a W in it.

 

Diesals are a different animal than a car. Modern diesals (built in the last 20 years) use the engine oil to produce the super high fuel pressures that they run on. Cold/thick oil will not flow well enough for the fuel system to work properly. Diesals need warm up in very cold temps.

 

The wine glass demo shown above is BS. To change the color of the oil by that much would require a high percentage of gasoline. probably 25% gas. For a typical car holding 4 quarts that would be a full quart over full with gas. At that point the cylinders would wash down and the car won't run due to lack of compression. A flooded engine does not run as much from lack of compression as it does from the fouled spark plugs.

 

Another internet waste of time


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#13
Johnny D

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So to come full circle...

 

Do you think you only need to warm up your car/race car for 30 sec or so because it's FI and has ECU ?

 

You're wearing out your race engine if you warm it up for minutes ?

 

Like the article said (don't kill the post man) Road and Track. I thought they were good, so hard to get good help, I believe everything on the internet.  :) 

 

Note**** not about diesel, puring any fluid, 80W, your tranny or any part of the car.***

 

J~


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#14
Erik Hardy

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The buildup for a race engine is generally much tighter than a street engine. The piston to bore clearance, ring end gap, and all of your oil feed bearings (mains, rods, camshaft) are generally tighter than your average econobox engine. If you were to start up a tight/fresh built race engine from cold and held it at WOT, you might seize it or begin scoring things. The true high performance engines have to run the oil pump to get the oil temp up to temp before startup! Production cars are loosey goosey and can tolerate these temperature swings better, with sacrifices in power.

 

Thicker (cold) oil has a higher shearing stress, that rapidly builds up heat at all of your journal bearings. If oil can no longer provide sufficient normal force (The rod bearings for example should never touch the crankshaft, they float on a thin oil film), The rod bearings will bottom out on the crankshaft and begin scoring. The more the rod bearings score, the greater the clearance, resulting in less oil pressure, which provides less normal force, less resistance to contact >>> see where this is going. This is why an old worn out engine usually has shit oil pressure at idle assuming the rest of the systems are fine.

 

Simply put, warming up your racecar with your super awesome freshly built engine is far more important than warming up your street car :)


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#15
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Everyone's cheater hub's spin like this, correct. Similar to your wine glass's Johnny.
Before anyone busts my balls, if the video had not stated REM'd I'd have never said cheater hubs.


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#16
Johnny D

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Thanks Erik, I'm wondering if anyone really read the article or watched the video....

 

the article said nothing about WOT and I'm sure that is an excellent way to blow up your engine and nobody would do that anyway, well maybe a idiot.

You're quite good at putting words in and/or changing things.

 

They said (in my 1st post) "just drive the thing" but I believe it said in the video a min throttle for a few mins or until warmed up.

 

If this thread is harmful I'll take it down.

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#17
Erik Hardy

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Personally, I think its all a trade off from wear. The OEM's have to protect for the bro's who start the car up when its wicked cold and go WOT. I would bet money that any OEM vehicle would do it all day every day from cold start and be fine. I think there would be noticeable scoring marks on the piston, cylinders, and journal bearings, after a teardown but "who-cares" if the engine continues to run. I would suspect slow degradation of oil pressure over time and some loss of power, which isn't the end of the world for production. 

 

The ECU can only derate the engine so much for protection, but with proper engineering, materials, and clearances it shouldn't be a problem.


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#18
Johnny D

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Ok, you guys win.

 

They used a new corvette as an example, it's not like that car has a race engine in it or that they race those cars at LeMans or any place.

We both have an engine that isn't optimum until warmed up/metal has to expand (not good). They suggest getting to optimum as gently as fast as possible.

You want to take longer to get to optimum by running your car at idle, fine. :peace1:

 

I can understand how this would be a bit tricky going from warming you car up, to pregrid and possible sitting, to the warm up lap/race and maybe leaving or not leaving the engine running.

Having it half warmed up not being good.

 

J~


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#19
Johnny D

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In my 40 years in the auto industry, w has always stood for weight. If it stood for winter, why would 120w-150 drag racing gear oil have a W in it.

 

 

I'm willing to beat you a free arrive and drive weekend in one of your cars. At a min. it stands for winter grade.

 

Any other taker ??

J~


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#20
Erik Hardy

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Well Johnny, I dont know how well you recall your fast and furious movie (Original) trivia, but Johnny Tran didnt waterboard his mechanic with winter grade oil! Lol
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