I get 13.5 mpg consistently with my 4.6iS with mainly Bay Area commute traffic. Lots of slow freeway time.

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2003 X5 4.6is Estoril Blue
2005 Infiniti G35X
1972 Datsun 240Z
1991 Isuzu Impulse XS Sold
1972 Fiat 850 Spyder Donated
1972 Datsun 240Z Sold
1972 Datsun 510 Sold