It won't hurt, but it won't help either. You'll be dumping an oil that is just getting up to speed chemically speaking, the formation of the anti-wear films finally stabilizing and doing a good job. Moreover, industry studies have shown that as the oil ages in service, the lubricity actually increases substantially. Ford study:
http://www.sae.org/search/?content-t...1-4133&x=0&y=0. So, you'll be replacing the 5k oil, that has a perfectly well-functioning additive pack, with a green oil that does none of the aforementioned nearly as well. It's a fact. Finally, there are apparently some data that shows that most of the formation of deposits in the engine occurs very early in the oil's use; again maybe a question of the oil's additive pack stabilizing, deposition lessening as the oil ages in use. This last info came from a lubricants engineer (Doug Hillary, well known on the BITOG oil forum) with decades of experience with both Castrol and Mobil in Europe (some of that time spent formulating oils used in BMWs).
Folks just can't seem to turn loose of the old conventional wisdom: it just common sense that fresh oil will do a better job of lubricating than aged oil. Well it was common sense for millennia that the sun revolved around the earth - - you could see it with your own eyes every day. Then science intervened.
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'14 328d, '13 M3 ZCP, '12 535i, '11 335d, '09 Z4 DINAN Stage II, '05 330i ZHP, '05 M3 ZCP, '02 M3, '91 328i, '90 535i, '88 528e, '88 M5, '87 M6, '95 Z3, 95 M3, '93 M5, '87 325e, '89 535i, '86 635i, '73 Bavaria.