The X1 is BMW's smallest SUV. Now, a good three years after its introduction, BMW has given it a much-anticipated facelift. Aside from minor touch-ups to the interior, the range of engines has been expanded. BMW's Twin Power Turbo technology has been outfitted with an eight-gear automatic transmission, an auto-start-stop function, brake energy regeneration and ECO PRO Mode, giving the new X1 greater fuel efficiency. Drive it! tested the biggest diesel, the 160-kilowatt BMW X1 xDrive25d.