It allows the engine to run on three of its six cylinders when loads are low, which improves highway efficiency. (driving.ca)
Surprisingly, the fuel efficiency of the XC90's V - 8 version is only 1mpg lower than the V - 6's EPA - tested city and highway efficiency ratings. (cnet.com)
Speaking of efficiency, at an EPA estimated 23 city, 34 highway, and 27 combined mpg, the BMW is has the same thrifty combined estimate as the Merc - Benz GLA250 4matic (gaining ground on highway efficiency, but losing it in the city). (cnet.com)