It's been a little over a year now since we traded in our 2006 Hemi AWD Durango. While there are still days that we miss it, we don't miss putting gas in it. We haven't needed the AWD (even with the snow days we've been getting) and we've made less interior space work. After at least 8 trips to NJ and back (280 miles one way) and a trip to Iowa, we've never not had enough room for both kids, the 75lb dog and all of the crap that we always end up taking. The 2.4L 4 cyl is able to accelerate the Mazda enough when needed. It isn't nearly as powerful as the Hemi, but then again, we don't tow with the Mazda (nor would we).
The numbers... Since I kept a fuel log of the Mazda from day one, I am able to tell exactly how much we've spent on gas. 17,921 miles driven, 672 gallons and $2,251 spent on gas. Lifetime average of the Mazda is 25.85 mpg (with a majority of those miles driven by the wife).
Total saved from the Durango is $1,884 and 562 gallons of gas ("$1,884ish", assuming 14 mpg).
So, while not exactly success by driving, it has been a success by a vehicle switch.
The bad part... We bought it new! Yes, we lost some money on it. We got a pretty good interest rate, but we owe a little more than it's worth. When we went to buy we looked at used Mazda5's. The new 2013's were on the lot, our 2012 was sitting next to another new 2012. The two used ones we looked at had 40,000+ miles and would have been only a few thousand cheaper. Since we were able to get the new 2012 for way under sticker price and had the full warranty (and two free oil changes), we decided that the depreciation was worth it. I will also say we are probably going to keep the Mazda for another 3-4 years, at least. Since we only paid a little over $19,000 out the door, the depreciation isn't that bad and we aren't complaining. Plus, my wife love's having a nice new car and she loves driving it. I know that warranties don't do much for new cars since new cars rarely need a big ticket item replaced, but it helps that we got it with 50 miles on it and know the vehicles history. I will keep up with maintenance and make it last. That will also be a plus when we go to sell it.
Overall, the vehicle change was a big success. There was little chance hypermiling would get that Durango to 25 mpg. We don't even have to think to get 25 mpg. Just though I'd share.
This is the lazy reason we don't take the Civic on road trips...