With the 2007 X5 3.0si, BMW carries on with an engine that countless fans have come to associate with the brand – the inline six. In this case, it's a 24-valve, dual overhead cam engine composed of magnesium and aluminum and featuring variable-valve timing. The use of relatively light materials helped engineers shave 22 pounds versus the 3.0-liter engine used in the 2006 X5, and also provided for marginal fuel economy gains (EPA-rated 17 mpg city, 23 mpg highway). Horsepower has jumped from 2006's 225 to 260 for 2007, achieved at 6,600 rpm. Torque has also increased, measuring 225 lb.-ft. at 2,750 rpm versus last year's 214 lb.-ft. at 3,500 rpm.