Lesser of Two Evils?

[Echo M3]

With the holiday season going on, I've finally had a chance to sit down and do my first proper read-through of the manual. I noticed a contradiction the other day, in the driving tips section - it states that one should not let the engine idle too long, yet it also says that one should not turn the engine on and off too frequently. Inevitably, there are situations that require us to do one or the other, for those of us that use our M3s as daily drivers or primary cars, i.e. unloading packages or dropping and picking up (those of you that live in the City understand what a hassle this can be). So I ask those of you with any knowledge on this issue, which is the lesser of two evils?

Oh, and happy holidays, before I forget

[///M Rakete]

Originally Posted by pman10

With the holiday season going on, I've finally had a chance to sit down and do my first proper read-through of the manual. I noticed a contradiction the other day, in the driving tips section - it states that one should not let the engine idle too long, yet it also says that one should not turn the engine on and off too frequently. Inevitably, there are situations that require us to do one or the other, for those of us that use our M3s as daily drivers or primary cars, i.e. unloading packages or dropping and picking up (those of you that live in the City understand what a hassle this can be). So I ask those of you with any knowledge on this issue, which is the lesser of two evils?

Oh, and happy holidays, before I forget

Don't have the manual so I have to ask: are they referring to idle at startup in order to warm the car up? If so extensive idling at startup is not good as it actually slows warm up and degrades emissions performance compared to starting, idling for say 10-15 seconds, and then driving off while not applying aggressive throttle inputs.

Traditionally starting an engine has been viewed has the most significant opportunity for wear given the reliance on whatever oil film still coats the internals of the engine. Of course the assumption is that the oil and engine are cold.

Personally I would suggest don't do either, long idling or repeated engine stops and starts. Avoid these as possible but do not trade one for the other either unless you know that the idling will be prolonged, say more than 5 minutes.

Just my opinion. In the end you have to drive and operate the car according to the circumstances that you encounter.

[JCtx]

To answer your question I prefer idling, especially if you're not going to drive at least 15 miles, to evaporate all condensation inside engine and exhaust, but I'm talking a few minutes max. Other than dropping a movie, some papers at an office, etc., if you have to constantly stop and wait like a taxi cab, the M3 is the wrong car for the job brother .

Contrary to what some believe, idling is not going to hurt the engine, hot or cold, but you need to 'exercise' the car regularly if driven under those conditions. People in large and border (int'l bridges) cities do it every day, and sometimes for hours. But idling on a thirsty V8 is not good for your wallet or the environment. Take care.

[///M Rakete]

Originally Posted by elp_jc

To answer your question I prefer idling, especially if you're not going to drive at least 15 miles, to evaporate all condensation inside engine and exhaust, but I'm talking a few minutes max. Other than dropping a movie, some papers at an office, etc., if you have to constantly stop and wait like a taxi cab, the M3 is the wrong car for the job brother .

Contrary to what some believe, idling is not going to hurt the engine, hot or cold, but you need to 'exercise' the car regularly if driven under those conditions. People in large and border (int'l bridges) cities do it every day, and sometimes for hours. But idling on a thirsty V8 is not good for your wallet or the environment. Take care.

+1. I would just add that I recall reading that 20 minutes at operating temperature is good to eliminate condensation. So 15+ miles in city driving is right on.

[niqui]

as long as you take care of the car, and judging by the fact that you are even asking this question - I am sure you are.
Dont sweat the small stuff, starting this car a few times vs letting it idle a bit more may not be ideal, but i assure you, it's not harmful.
which is worse? Depends on the situation.

[SenorFunkyPants]

Probably not applicable to your situation but worth remembering.....stopping and starting the car several times in succession when the engine is cold is not a good idea (or repeatedly cranking the car over when it won't start). Unburnt or poorly burnt fuel can damage the catalytic converter.
Anyway I work on the principle that if the trip isn't long enough to allow the M3 to fully warm up then I take the wifes car!

[Leozap]

Originally Posted by ///M Rakete

+1. I would just add that I recall reading that 20 minutes at operating temperature is good to eliminate condensation. So 15+ miles in city driving is right on.

So I am screwed then. I live 5 miles from my job and that's pretty much less than 15 minutes driving.

[///M Rakete]

Originally Posted by Leozap

So I am screwed then. I live 5 miles from my job and that's pretty much less than 15 minutes driving.

I would just say that you have a very good reason to take the car out once a week and enjoy it, put a few miles on it, give it the beans (your foot). As long as you burn off the condensates once a week or so I don't think it's going to be an issue. The good news is you don't have a 5-series, you wouldn't be driving enough to keep the battery charged and you would have power management issues, active steering initialization issues, ...

[JCtx]

Originally Posted by Leozap

So I am screwed then. I live 5 miles from my job and that's pretty much less than 15 minutes driving.

If you don't take the long way home, at least every 2 or 3 days, you're going to eventually rust your engine (and some parts of the exhaust) to oblivion. Remember the M3 takes longer to evaporate condensation than most cars due to 9 qts of oil.

[Echo M3]

Thank you for the feedback, it's most appreciated. I'll to avoid either, but if I'm forced to be in this sort of a situation I will probably just let it idle. As someone noted, I plan for this car to be a 'keeper' and I would like to take as good care of it as possible, while still enjoying it and flexing it once in a while .

Cheers

[BCA]

Originally Posted by elp_jc

If you don't take the long way home, at least every 2 or 3 days, you're going to eventually rust your engine (and some parts of the exhaust) to oblivion. Remember the M3 takes longer to evaporate condensation than most cars due to 9 qts of oil.

Just curious...do you know this for sure or because of some training you have, or is it just what you think based on what you've read, heard, etc.? I'm not disagreeing with you, I'd just like to know a little more about this because I'm in a similar situation. I live about 6 miles from work and the trip takes about 15-25 minutes normally depending on traffic, with several red lights. The engine (at least the oil temp) does normally get all the way up to operating temp during the trip, but I still may start taking the long way home occassionally if you convince me that it's necessary to prevent engine/exhaust rust. I've always thought that my trip was plenty long to burn off condensation, but maybe not...

Thanks!

[meevo]

short driving's not good for any car. it's to do with the oil not getting hot enough

[BCA]

Yep, I know (and have known) that short trips aren't good. But I was surprised at the statement that 15 minutes isn't enough driving. With my drive being 6 miles or so and normally 15-25 minutes, the oil temp always shows near 210 by the time I arrive at work and I've always figured that's good enough.

I'm hoping that someone with technical knowledge can chime in with a good estimate of exactly how much driving (in miles and/or minutes) is "enough" for our engines with their ~9 qts. Or maybe no one really knows and it all just depends on driving styles, weather conditions, etc. and the best we can do is generally estimate. I did a little searching online and I saw "15 miles" mentioned a time or two as a minimum trip length to avoid rust issues. I sure hope that isn't the case because I rarely drive 15 miles at at time...