Quote:
Originally Posted by Peter7307
The roads are flat and the cruise is on which recirculates some of the exhaust gas as well as holding the throttle steady.
There may be a lean burn factor cutting in under these conditions as well.
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I think you are right. There is less load on the engine, but it is too close to idle and so uses more fuel! Pulse and glide at the slower speed is pretty much always more efficient though, but probably not something to try in an auto.
See this page
here.
EGR is typically not employed at high loads because it would reduce peak power output, and it is not employed at idle (low-speed, zero load) because it would cause unstable combustion, resulting in rough idle.