With all this dicussion of "minimizing pumping losses"

[fumesucker]

Originally Posted by *************

It's interesting to see everybody advocate P&G yet isn't it conventional wisdom that cruise control saves gas?

P&G is not the same thing as random speed variations, which is what a cruise control is designed to minimize..

P&G is more along the lines of how some hybrids operate, where the engine only runs part of the time at full power for just long enough to recharge the batteries/pump up the accumulator/whatever..

If you look at the BSFC map of a Prius engine below, you will see that at high loads, above 70 Nm or so the engine uses less than half the fuel per kilowatt hour than it does at low loads of 15 Nm at the same 2500 rpms. 230 g/KWh versus 500 g/KWh.

If you don't understand what you are seeing looking at the BSFC map below, you really need to do more studying before we can properly relate the concepts that some here are trying to explain to you.. There are a lot of things in life that are counterintuitive, and this is one of them..