Warming up your engine

[pundit]

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? ...

I didn't notice that Bill suggested to redline the car when cold.
Moderate smooth driving is all that is required for the first few minures.

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...

Warm up time requirements have tended to change over the years for a number of reasons. There were (in some cases still are) valid reasons for allowing an engine to 'warm up' before driving off. For instance many older carburettor fitted engines would often hesitate and sometimes stall until a certain operating temperature was reached. Nothing worse than pulling out into a break in the traffic to find your 'cold' motor has suddenly cut out and a semi is bearing down on you! Not so with most fuel modern injected motors. They should run reliably, without risk of cold stalling, right from startup. Also older (thicker at low temperatures) non-synthetic oils don't flow as well as modern multigrade (synthetic) oils and could often take sometime to pump through to all areas of the engine. With oil grades now commonly starting around 0w, 5, or 10w the oil flows much more quickly to all parts of the engine at low temps so the risk of oil starvation, and associated wear caused by 'thick cold oil' is greatly reduced...

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...

I don't think anyone is suggesting that running an engine at excessive revs (above say 4000 etc) when cold is a good thing. Potential (cold) oil starvation has already been mentioned. However letting it sit idling for ten minutes is not the best option either, option b) is the most sensible.

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!..

Air flow through the radiator of a cold engine has negible cooling effect until the thermostat opens and allows coolant flow.... unless of course your thermostat is stuck open or has been removed.

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!...

I would think that in reality many people will often run the engine for a minute or two before they drive off even if they say they don't 'warm' it up. This is especially true at first start up in the morning. From my own perspective I wouldn't say I warm my car up but I get in, start the engine, turn on the radio, adjust the volume, put on my seatbelt, check my mirrors, reverse back around to the side of of the house then forward up my drive and out into the street. I don't get out of 2nd gear or even to 2000rpm's until maybe two minutes after first start up so I guess you could almost say this is my 'warm up' period, even though I'm actually travelling somewhere while it's warming up.

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

I think the validity of an extended idle warm up periods with modern engines and lubricants is a thing of the past, and offers no real benefit in terms of engine wear or longevity compared with a sensible 'start and drive off' approach. Granted extreme revs or engine loading when cold is not a good idea, but remember that engines are designed to spend the majority of their life at operating temperature and those engines that last the longest (ie. taxis etc) spend most of their life running at optimal operating temperatures, and any automotive engineer will tell you the longer an engine spends running at sub-optimal operating temperatures the greater the engine wear.

[liquidtiger720]

I think, in my case...I need to let it warm up a little before I take off. I have a bIG BIG hill that I have to overcome right up the block from me...I usually go up that hill at 15-20mph because I dont wanna go over 2000rpm. Anyways...when I leave school, I have to get on the freeway, which is about 1 block from the area I park near. This particular freeway is a two lane freeway, and you have to merge within 100 yards of getting on the on ramp. Its hard doing that and keeping the rpms under 2000. I would end up cutting off traffic that is going 65+ in the slow lane. So, maybe different strokes for different folks?

[Robin-535im]

I just think the fear of letting a car idle a bit is silly.

I didn't notice that Bill suggested to redline the car when cold.
Moderate smooth driving is all that is required for the first few minures.

Being facetious of course... but if "warming it up the fastest" is the primary metric of engine health, stands to reason that bouncing it off the rev limiter will be the optimal solution!

[Kalevera]

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

How long's that been going on? It sounds like the oil pump isn't working efficiently -- have the oil pump bolts been checked?

best, whit

[pundit]

I just think the fear of letting a car idle a bit is silly...

I'm not sure I get your point? Who's in fear here? If there was a benefit in an extended idle warm up period then I'd say by all means... "Start engine, let idle for five or ten minutes, then drive away!"

I gather your motivation for starting this thread was a belief in a starting (warm up) method that was the most beneficial ie. least harmful to your engine. I think we all want what's best for our engines... don't we?!! I don't disagree at all about avoiding excessive revs, or loading on a cold engine.

Traditionally the school of thought has been to always start your engine and let it warm up for a few minutes before driving off. In fact a friend of mine used to start his car, go back inside the house, have a coffee and then come back out and drive off. He owned a 1964 EH Holden Premier 179. (Most Aussies will know what I'm talking about here!) This old school of thought was, back then, often quite a valid one. Unlike modern oils, the time taken for the oil to reach all parts of the engine at first start up would have taken longer than with modern lubricants, hence not a good idea to rev the hell out of the engine at this point. Also was the problem of fuel not vaporising properly and condensing inside the walls on the inlet manifold of a cold carburettored engine. Having the choke at three quarters whilst pumping the accelerator like hell to ensure enough fuel got into the cylinders tends to dilute the oil film on the cylinders walls reducing the lubricating effect, also increasing wear. These two things alone could definatley accelerate engine wear if one simply drove off with a stone cold motor, like a lunatic at high revs, pumping the accelerator like and before the bearings had received enough lubrication.

The two main causes of engine wear at initial start up are greatly reduced in vehicles fitted with correctly operating fuel injection systems and modern free flowing oils compared to the 'norm' of say 30 years ago or more. So if cold starting lubrication and oil dilution problems are now much less of an issue, which they are, then more benefit will be gained by a sensible 'start and drive' approach than a 'sit and idle' approach. Besides in the five minutes I'd waste letting the engine idle, I could have driven 5kms (3 miles) that's say twenty times in total per week. So in the time I was sitting waiting for my engine to 'warm up' each week I could have driven 60miles while it was warming up!

Being facetious of course... but if "warming it up the fastest" is the primary metric of engine health, stands to reason that bouncing it off the rev limiter will be the optimal solution!

Well if I applied that logic elsewhere I should be able to consume half a ton of viagra and become the biggest stud on the planet!

[Robin-535im]

I'm not sure I get your point?

I think that's where I lost you... you were assuming I had a point??

You are spot on my friend. I agree with all of it. In fact, I don't think I ever said it was a good idea to let it idle, just that it wasn't really a problem to let it idle a minute or two.

Geez - I seem to recall some post a while back where someone was really opposed to letting it idle at all, and I thought, "well, that's silly - there are worse things you can do."

In fact, it's so not worth worrying about that I feel guilty for typing so much in this thread! Bring on the weekend!!

BTW - someone really needs to take some data on how long it takes to warm up the engine water and oil at different RPM levels. That would be interesting to see.

And I think I'll try that viagra thing you were talking about...

- Robin

[Randell]

i let mine idle until i see the needle has moved off zero.. then i just drive under 2.5k rpm until it hits halfway, then it flog it!

i never just start a car when stone cold and drive it, after driving an old carburetted 4 cylinder toyota you learn not to do things like that..

[Jay 535i]

Toronto police will give you a ticket if they catch you idling more than three minutes.

[genphreak]

3 Mintues and they book you? Maybe next year they will book you for idling for 2 minutes, then at next year for idling at a stop light- then approaching the speed-limit on a 5 lane deserted highway.

Aww hell in Sydney they do that last one already

Well if they book you for idling in some jurisdictions the owners manuals could never be written in such a way as to promote the idea of warming an engine up.

Personally I let it idle a little- perhaps 10 seconds before engaging first. I crawl up hills on light throttle and don't let it change up unecessarily, nor do I rev over 2500 during warm-up. I don't go Wide Open Throttle much (or anything like it) but never within 15 mins of starting out.

Everything in moderation my mum says.... I've learnt that driving is a good example of it.

What I do know is that the engineers design engines for fast warm-up (for a damn good reason; we are (mostly) short of time to wait!).

I for one am glad they do.

GP

[nuwde]

so what's your take on remote starters?