What do you hope to gain with an additive? It won't fix anything. It may make the oil thick enough to sell the vehicle quickly to an unsuspecting buyer.

Oil pressure rises with rpm. At low rpm you naturally have low pressure and the engine condition is making it worse. Fix it, live with it, or sell it.

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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