cams and mpg

Just in general why do cams decrease gas mileage?

 

choppy cams*

 

high lift cams allow for more flow, more air needs more fuel

 

My knowledge is based mainly off of American muscle; the [awesome sounding] 'lopey cams your thinking of added lift and changed duration. Some shifted the timing of the valve openings a hair. Chain sprocket could be swapped to advance/retard valve timing... (close your eyes; remember the sound of an American muscle V-8 with a lopey cam, and glass-packs Now tell me you can't smell something based on the memory of a sound )

All this to increase power and almost always in the mid to upper range. At the expense of low end (not to mention vacuum at idle) requiring more pedal in town and higher RPMs in general.

The MOPAR "Purple Cam" [and other mods] on my 440 required a bump to ~900 rpms iot run...

Not to mention, anyone doing a cam swap is definitely doing some other mods that cannot be MPG friendly... Thus more pedal and higher rpms = lower MPG