I have a new Honda Odyssey that shuts off three of the cylinders when cruising. So far in town I'm getting 22 mpg in city driving which is pretty good for the large family truckster. Haven't tried it on the highway, yet. The shutting on/off of the cylinders is seamless too, with no associated noise, vibration or surge.
Big deal, I had a Gremlin that did that back in '75 (g)