Because 5000klm is not enough to run the diesel motor in, it takes about 12,000klm. Also at that stage put a new air filter in because BMW only swaps them out every 3rd service and clean air is important for a diesel. I gain 1 & 1/2 ltrs better economy with just a new air filter.

Also 21" wheels are a large amount of mass and it will cost you a litre per 100 with them.

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