Warming up your engine

[Robin-535im]

Nothing bad happens (aside from "wasting" gas) from letting your car warm up at idle. Nothing.
(EDIT: okay - I admit - I said this a little too emphatically in an attempt to shake things up on a slow afternoon. Don't hate me. It's sub-optimal, but not inherently evil, to warm a car to completion at idle... but there are dozens of other ways to cause a lot more wear. Read my other post - I said it better there. )

I say "wasting" because it's a teeny bit of gas relative to how much it takes to actually move your car down the road.

Bad MIGHT happen if you let it warm up at idle until the water temp indicator says it's warm, then flog the hell out of it... but the point is that "water temp warm" and "engine and drivetrain at operating temp" are different things.

What you want is for the drivetrain to be at operating temp before you stress it, where stressing it is applying large loads (flooring it or going high-speeds, EITHER RPM or MPH)).

You could warm the car with a heating blanket. You could park your car in an oven. You could let it idle - but idle doesn't heat up the gear boxes so if you let it idle to warm up, the whole drivetrain is not ready for flogging.

Car manuals are written for simplicity and clarity... the easiest and safest way to describe warming up is not to go into the details of operating temps of the gear box etc. etc., but just to say "Idle - bad. Drive - Good!"





Just had to get that off my chest. Wheew. Feel better now.



- Robin

[632 Regal]

excessive idling when cold can build up more carbon since its running rich when cold. with that there is the problem of excess buildup on the 6's where you have to clean that crap out so you dont get detonation (spark knock) and if you raise the rpms right from the getgo it will warm faster and have less carbon buildup.
I take off about 5-10 seconds after I start the car and have a mile where i can really drive easy before i have to accelerate to 55mph. To just fire it up and go blasting up to and at 55 just doesnt sound healthy to me.

[Bill R.]

warm up, its that it increases wear. The manufacturers all advise you to drive away shortly after starting to promote rapid warmup, It warms up quicker this way and the parts expand to the proper tolerances faster, reducing wear. If an engine sits and idles to warmup it takes longer to get warmed up to operating temperature. The greatest amount of wear on any engine is during the starting and warmup period, so by driving it at a moderate pace, you warm up the engine much quicker.

Nothing bad happens (aside from "wasting" gas) from letting your car warm up at idle. Nothing.

I say "wasting" because it's a teeny bit of gas relative to how much it takes to actually move your car down the road.

Bad MIGHT happen if you let it warm up at idle until the water temp indicator says it's warm, then flog the hell out of it... but the point is that "water temp warm" and "engine and drivetrain at operating temp" are different things.

What you want is for the drivetrain to be at operating temp before you stress it, where stressing it is applying large loads (flooring it or going high-speeds, EITHER RPM or MPH)).

You could warm the car with a heating blanket. You could park your car in an oven. You could let it idle - but idle doesn't heat up the gear boxes so if you let it idle to warm up, the whole drivetrain is not ready for flogging.

Car manuals are written for simplicity and clarity... the easiest and safest way to describe warming up is not to go into the details of operating temps of the gear box etc. etc., but just to say "Idle - bad. Drive - Good!"





Just had to get that off my chest. Wheew. Feel better now.



- Robin

[SRR2]

Maybe it's off your chest, but NOT ONE manufacturer that I've ever seen who has expressed a position on the subject, agrees with you. I challenge you to cite one owner's manual that recommends starting and idling up to temperature. As far as your dismissive "manuals are written for simplicity and clarity", I don't see where this has anything to do with anything. The owner's manual is basically a legal document that sets out manufacturer-specified operating procedures and parameters of the car and corresponding owner's responsibilities. Operate outside those parameters at your own risk, up to and including loss of warranty coverage.

[Anton CH.]

I agree with Bill. Just drive it normally, keep the RPMS below 3.5k and it will warm up on its own.

[MantecaBMW]

....so I let mine warm up about 5 minutes in the morning until it shuts up....then I drive

[bahnstormer]

keep in mind that it may take 15 min of driving to get the oil temp up to par
it wont lubricate if its too hot or if its too cold, and also keep in mind the water
temp gauge (coolant temp gauge) doesn't tell u the oil temp =]

[Robin-535im]

warm up, its that it increases wear. The manufacturers all advise you to drive away shortly after starting to promote rapid warmup, It warms up quicker this way and the parts expand to the proper tolerances faster, reducing wear. If an engine sits and idles to warmup it takes longer to get warmed up to operating temperature. The greatest amount of wear on any engine is during the starting and warmup period, so by driving it at a moderate pace, you warm up the engine much quicker.

Well - we can agree to disagree... by your logic we should all redline the car immediately upon starting so we can warm it up as quickly as possible?

Driving will place a load on the car, and a loaded car suffers more wear. Alternately, like you said, time spent at a sub-optimal operating temperature causes wear. I will defer to the engine manufacturers if they say that the latter outweighs the former in some cases, but not all.

We know that the M5 rev limiter goes up as the engine reaches operating temp. That says that at some level, loading the engine when cold is bad. Where is the real cutoff? Should you: a) let the car idle at 800 RPM, b) putter around at 2000 (probably yes) or c) really heat it up fast by running it at 6000?

Point is there are conflicting effects here, and the truth is not so simple as "warming at idle is bad." Is it sub-optimal? Probably. Can you do a lot more harm by high revving your cold car than by letting is sit at idle? You bet. Can we ever really answer this problem without a test that accounts for all the factors? No. Is this my Donald Rumsfeld impression? Sure is.

All driving does to warm the engine faster is to rev it more - the motion doesn't make the car warmer, in fact the motion adds cooling via air passage, unless you live in one of those places where the ambient air is over 100!

I'm not promoting letting the car idle until full warm, but I think it's wrong to scare people into driving off immediately instead of letting it idle for a minute or two if they want. In fact, I maintain it's better to idle for a minute and then drive normally than to simply start the car and drive normally, if "normally" means you drive like most of us do: with enthusiasm!.

Bottom line is that it's way more complicated than can be summarized by "warming at idle is bad", and the differential wear of warming at 800 RPM vs. warming at 800 - 2000 RPM is (I believe) negligable compared to the wear caused by running at high RPM's (which we all do), letting the oil sit unchanged for the complete BMW_recommended service interval (which heaven forbid any of us do) or having a sensor or part out of spec. To worry about warming the car at idle is like polishing the brass on the titanic, if I can borrow a quotation from Fight Club.

But - I welcome disagreement!!

- Robin

[Robin-535im]

Maybe it's off your chest, but NOT ONE manufacturer that I've ever seen who has expressed a position on the subject, agrees with you. I challenge you to cite one owner's manual that recommends starting and idling up to temperature.

Well - I sure don't recommend that either! And just to keep the tone happy, I've sprinkled happy faces throughout. The point is that "idle-bad, drive-good" is an over simplification. Wear is a function of operating temp, lubricity, clearances, loading, etc. Blindly following a simplification without deeper understanding of the real issues is where you get into trouble.

As far as your dismissive "manuals are written for simplicity and clarity", I don't see where this has anything to do with anything.

A manual that got into the details about engine load and operating temperature etc., would never be read and understood by the average driver. The purpose of the manual is to maximize the ownership experience by effectively communicating the basics. Get too complicated and people don't care to read it. Hence, they simplify things to get the point across. Idle = bad is a simplification.

The owner's manual is basically a legal document that sets out manufacturer-specified operating procedures and parameters of the car and corresponding owner's responsibilities. Operate outside those parameters at your own risk, up to and including loss of warranty coverage.

I don't see where this has anything to do with anything.

Okay okay - not trying to cause trouble. Just trying to make a point. Car enthusiasts like ourselves owe it to ourselves to know more than average about what really goes on inside our engines.

[Paul in NZ]

i idle while i put on my seat belt,wait a few more seconds until the SI lights go out and then i drive......I am pretty light on the throttle any ways.....,i ussually have to take off uphill i always grimace a little as I rev her up a bit in first.......