Generally, if you use good quality fuel (with sufficient additives/cleaners) you don't need it. If you have buildup of deposits in your injectors, it can help restore smooth running.

Chemically, it is reported to be Techron, also available from Chevron retailers.

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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