Not exactly the most scientific testing in the world, but had me wondering after my dad mentioned it to me when they came down this past weekend.
Example 1:
My 2013 SHO has about 6700 miles on it and I've been back and forth to NJ from MD (about 135 miles one way) quite a few times with the cruse control set at 75-80 MPH. I'll get out of the gas station right before getting onto I-95 and reset my MPG reading on MFT when I hit the highway. I know when you do this at first you get an inflated number then it settles down into the proper MPG range. Well when I do this in the SHO, it reads about 27 MPG (a bit higher then the MPG ratings) then for the next 75 miles, it keeps dropping and dropping till it settles out at anywhere from 20-21 MPG, which is quite a bit lower then EPA ratings of 25 MPG, which I've only been able once to hit with the car. I get about the same MPG ratings for the car driving around town. I releaze that the Ecoboost engines are throttle sensitive (if I gun it I can kill the MPG by at least 2)...but I can't figure out why it keeps dropping MPG with the cruise enabled.
On two non-ecoboost engines making the same trip, a 4.6L V8 with nearly 120K miles and a 3.0L V6/AWD with 95K miles on it, doing the same trip, they will start reporting higher mileage, then only maybe drop a MPG or two and not go lower till you start doing around town driving and getting their MPG ratings or even better doing the same drive.
Example 2:
My parents have a '13 Escape Ti with a FWD 2L Ecoboost engine in it. They drove down to my place, and more or less did the same thing I did...got gas, reset the MPG counter and drove down doing 70 MPH using the cruise control. My dad reported getting about 29 MPG at first, then by the time he got to my place, he was only avg about 24 MPG. They didn't hit any major traffic or anything, nor where they using the AC, which my dad says has a major impact on his MPG's with the Escape (and I get most other 4 cyc engines)...he also made it a point to drive very conservatively to get the most out of his MPGs also. The only issue I think he might have is he only has 3500 miles on his Escape, so it could be still breaking in.
Has anyone else ran into a issue like this with their Ecoboost engine? I know the MPG counter in the dash isn't the most accurate thing in the world, but getting 20-25% less then what the EPA MPG estimates is a bit disconcerting.
