Agree with Judge on gas being cheap, but for me MPG would be important because it also affects driving range. The standard Transit gas tank is only 25 gallons, which is what Thor lists in specifications.
The joke about EcoBoost technology has been that it’s Eco or Boost, not both at same time. That should be expected though. You’ll get V6 economy when driven conservatively, and V8 power and corresponding fuel economy when heavy on gas pedal.
Transit EcoBoost motorhomes haven’t been out very long yet, so you will probably not find a lot of fuel economy data. However, I think MPG should be very similar to equal-size Transit motorhomes with standard V6 gas engine. Those have been around for a few years.
When I looked into them previously, reports typically ranged from 12~14 MPG depending on driving speed; assuming no towing.
At about 12 MPG it would give a driving range to empty of 300 miles, which is on low side for most motorhomes, but still provides over 3 hours at interstate highway speeds.
P.S. — Please report back with your own MPG when available. I’m certain there will be much interest.