I would think that small a variance would be OK.

Since you don't mention it, I have to ask. You have reset the tire monitor after setting the pressures correctly, haven't you?

If so, then consider getting the new tire shaved down to the same tread depth as the other three tires. Cheaper than buying three more tires.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue