In my experience with cc, maintaining an exact speed is more work for the engine.. You can adjust to a lower speed on a hill to keep rpm down, accepting that its a hill. On declines you dont motor brake.. being eccentric, i think of cc like a nanny for a kid.

 

i'll use cruise control on flats.

on my commute, I do use it, but on hills I turn it off and go manual mode. for down hills, i use that chance to build up momentum .... and use it to sling shot myself up the next tall hill

 

I generally don't have a hilly commute ~100km each way, elevation doesn't change more than 100m vertically over the whole course.

https://kurviger.de/en?point=45.2115...Esri%20Streets

 

Thought I replied to this one. If the hills are minimal it doesnt seem like itd be that big of a deal but do imagine its just more work for the car to maintain a constant exact speed.
three repeat tests with the same results would make it a theory, right? Or is that a hypothesis... either way
also I think stickier tires would decrease mpg.. but hard tires are less safe. Can check wear ratings. The numeric scales vary based on manufacturer, but you could still get an idea looking at a few from each one. The cheeeap tires will be harder. Right now I'm riding michelin pilot a/s 3s on 16x7 sparcos with a +35 offset. I dont think its messed up the scrub radius. Theyre a performance oriented middle ground with a 50k warranty. One thing I can say is, despite the AA traction rating their definitely more responsive than the fancy yokohama S-drives I had before, and my mpg has increased since the change.
still working on getting my average mpg down to 26, right now at high 27s.

 

Re: Fuel economy, hills, and cruise control

My commute has a really hilly interstate where people expect you to go at minimum 60, preferably 70+. Ive noticed that using Cruise Control is not very efficient at all for this part of my commute. I often get 3 or 4 mpg less. Not to mention that almost no one else uses cruise control and going up hill people will slow a bit, so youll be more wit the flow. I average about 28-30ish right now on this stretch. i95 is flat though so I can easily get 34ish at around 65-70.