Winter is upon us in most parts of the M3-driving world, and one of the more relevant questions of this season has to do with pushing a cold motor hard.  Because of the technologies involved in the S series powerplants, this is a particularly important matter for ///M car, and yet, relatively few owners seem to understand how to properly bring an engine up to operating temperatures -- much less why it is important.  Given that close-tolerance, race-derived motors like the S54 are particularly vulnerable to this kind of damage, a quick 101-level review is probably in order.

Central to the discussion at hand is the matter of piston speeds.  BMW has stated repeatedly that the S54 can achieve redline piston speeds approaching that of a typical Formula 1 race car (24 m/sec. for the S54 versus 25 m/sec. for the F1 race engine).  A simple understanding of basic metallurgy tells us that subjecting cold metals to unusually rapid warming cycles at high rates of speed is a sure recipe for premature fatigue.  Beyond this, one has to consider the very different expansion rates of the aluminum pistons and the cast iron block.  Unless these components are allowed to reach operating temperates gradually under only moderate loads, design tolerances can be easily exceeded, resulting in dramatically accelerated component wear.  Or worse. 

At least part of the larger problem here has to do with the tachometer "warm-up" lighting systems which first appeared in the E39 M5.  Whereas cautious drivers in earlier-generation ///M cars were generally in the habit of watching engine temperatures and restricting RPMs on a cold motor, the new warm-up lights have reduced the requirement to simply watching a succession of multicolored lamps.  The correlation behind what is actually happening under the hood has been all but lost.  What's worse, these warm-up lights tend to be set rather generously, calling more attention to minimal safe limits than what is actually best for the motor.  As such, they really should serve as little more than a reminder to keep an eye on things, as a bit more conservatism is probably warranted in the best interest of the engine. 

To illustrate this point, consider the following recommended limitations for the S38-powered E34 M5 (3.8 liter). 

E34 M5 (S38) Placard Limitations
OIL TEMP	RPM	THROTTLE
50c	3000	1/2
60c	4000	1/2
70c	5000	3/4
80c	6000	Full
90c	Full	Full
Normal Eng. Oil Temp range is 95c -105c

In general, you can see that even moderate engine loading (say, 5,000 RPM) is contingent upon reaching an engine temp that would register at roughly the 1/4 mark on the associated gauge.  Full RPM and full throttle are avoided until the motor almost totally warmed-up.  While the applicability of this chart is not necessarily direct to the newer S54, I believe that common sense dictates that a similar regimen will almost certainly have a profound effect upon engine longevity.

If you live in an area where the winter temperatures routinely dip to the freezing point, do you take your engine temperature into consideration when you start out for work in the morning?  If not, consider the cumulative effect of this oversight as the end of your warranty period draws ever closer.  Can you really afford to be wrong?  Obviously, for me the answer is a bit of conservatism -- even to the point of cruising in the right lane of the autobahn for a few minutes, when necessary.  :)  The point is this: whether or not you plan to have your M3 sitting in the garage five years from now, learning to pay attention to details like this make you a better driver ... and who among us doesn't aspire to that?