Hi Tom,
Welcome aboard. We have a C-Dory, not a Ranger Tug, but I hope I can add to the discussion. We were sailors before considering the change to powercruising... and had a certain bit of angst about making that change. With our trimaran, we could run all season (sailing daily) for about $15; only used the motor to get in and out of our canal. Depending on where you want to go, you will certainly use more fuel with a powercruiser. Of course, there are some parts of the country where the conditions dictate that sailors will often be motoring, as well.
When we decided that traveling with a boat would be a part of our retirement plans, we committed to the powercruiser way. Much like sailing, it's about options: go faster and you will burn more fuel, slow down and it drops the burn and greatly increases your range per tank. And something you have probably considered: the enclosed helm is wonderful. I enjoyed being out in the air when sailing on our different boats, but I could not go back to that after having an enclosed helm. Wind, rain, cold, or scorching sun - it doesn't leave you wiped at the end of the day. And you still have a cockpit to kick back in for those sunsets. Our boat is easily trailerable (part of the reason we bought it), and I know some folks here tow their Ranger 29s. When you get to new cruising areas (at 60 mph instead of 6), it only takes a few minutes to launch, and you are off to enjoy the water... another great benefit.
I had concerns that we'd lose our sailing buddies, but that was not the case - most of them were intrigued by our change (we also kept a sailboat for a couple years after buying the C-Dory). When we ordered our boat, from Jeff Messmer (aka Ranger Jeff here), I told him my concerns about losing our sailing friends... I still chuckle when I remember what he said, "You will make new friends." Turns out he was absolutely right - our circle of friends is ragbaggers and stinkpotters. 😉
Addressing your fuel burn question: you will use more fuel, assuming you spent a good portion of your time onboard under sail. It doesn't have to eat you out of house and home (or boat). Instead of thinking about it as 3 mpg or even $1 per nautical mile, I think of it in terms of fuel burn per hour... and the cost of running my diesel pickup is about the same as our boat in terms of fuel burn per hour (at mid-cruise speeds). Plus, we get amazing smiles per gallon.
Plus, you will save a ton of money by not having to buy new sailing gloves and updating your foulies... it's mighty comfortable cruising in shirtsleeves when the rain falls and the cold wind blows.
Good luck with your decisions.
Best wishes,
Jim B.
