I've read (I think it was on slashdot) that using constant velocity cruise control on your car is much more energy efficient than letting your speed vary. To the point where they said you would want to control your speed to much less than 1 kph. What is the general consensus on this? I'm a little skeptical. If you're constantly fighting the effects of wind, friction, road topology, etc. what is so special about constant speed? I would think constant throttle may be more efficient. Or even a more complex throttle pattern. Maybe one that is inverse with the road resistance. I'd expect it's a throttle pattern, near the speed you'd like to travel, would keep you at peak engine efficiency, rather than constant velocity. I guess my question is, can you predict behind the driver's wheel what is the optimal throttle or is constant velocity the safest approach. Anyone have any comments? P.S. To add to the discussion and also partly my confusion. I also read somewhere (I think it was a BMW test) that your peak efficiency is at 60% of full throttle. So maybe an ideal driving pattern would include throttling at 60% for the longest time?