The Jaguar XJ has a lightweight aluminum body structure, but until now its gas mileage has only been middling.
The addition of a six-cylinder engine, stop/start, and an eight-speed automatic brings much better highway gas mileage potential to the Jaguar XJ--if you can control your baser urges.
Doing the math is simple. Last year's entry-level XJ V-8 was rated by the EPA at 16/23 mpg; this year's supercharged six is pegged at 18 miles per gallon city, 27 miles per gallon highway, or 23 mpg combined.
Adding all-wheel drive, whether you're in a short- or long-wheelbase car, drops those figures to 16/24 mpg or 19 mpg combined.
The normally aspirated V-8 still is available in 385-horsepower form, now teamed with the more efficient eight-speed automatic. So paired, the 2013 XJ earns EPA figures of 16/25 mpg, or 19 mpg combined.
Finally, opt into the supercharged V-8s--either the 470-hp or 510-hp, short- or long-wheelbase versions--and gas mileage is 15/23 mpg, or 18 mpg combined, up a single mile per gallon highway from last year's numbers.
The XJ's stop/start system is one of the happier ones in the automotive universe. In bitter-cold driving, we only experienced it a few times, but it cycled on and off with a barely perceptible quiver.