Quoting myself from another post, on another day, because today I'm feeling decidedly lazy
"Run in procedures are a pain in the backside. Everyone's got different opinions, and even the guys that design them have differing ideas about it than the guys who build them, maintain them, tune them, or prep them. The universal, agreed by all concerned, no questions, do-not-pass-Go-and-do-not-collect-£200, absolutely must avoid thing though. Is do not give it the beans until it's fully warmed through.
Avoiding constant speed and load seems to be a common theme too, not often mentioned as it's not easy to do on road cars, but its emphasised quite a bit in marine engines, which experience constant speed and load routinely.
Other than that, it's appears that anything else is fair game. I've a number of friends in the motor racing, motor journalism, and new car development games, and it seems the best engines are the ones that have been warmed through and then let off the lead straight away. Something to do with getting maximum combustion chamber pressure behind the piston rings early on and bedding them into the bores before all the honing has been worn smooth. They have a wide variety of high profile successes between them, especially in endurance and GT racing where long term reliability really counts, so I think I can trust their judgement. The jury remains out when it comes their judgement in women, fashion, and appropriate jokes for a best mans speech though.
Of course if your aim is to prevent damage, then you've already missed the boat on two counts;
One, these engines are built to quality levels and tolerances that were considered impossible to achieve even 15 years ago, so they no longer need the running in routine that older cars had to have. They're very very good already.
Two, by the time you get your hands on your pristine motor, it has been banzai'd from stone cold for an against the clock time trial on at least six occasions by a specialist nutcase who's task in life is to get your car and several hundred others from one point to another with the sort of speed and precision not seen since Russ Swift did the Montego ad for Austin back in the '80's.
It has been whipped off the production line to a waiting area, from a waiting area onto a train, from the train to a car park, from the car park onto a ship, where it would have been parked so close to its neighbour you could have clamped a Rizla between the wing mirrors. Then, when it got to the UK, some bloke from Grimsby blasted it off the ship to a car park, before loading it into a truck with similar speed and similar lack of mechanical sympathy a couple of days later.
If it was going to break through some latent engine build defect, chances are it would have done so before it got to the dealers."
