Chuck, your numbers crunching for savings of gas vs. diesel and mileage is something I think not everyone does. While I too consider that, I haven't really done any serious number crunching. I realize with a diesel you also have higher maintenance costs and definitely upfront costs. I have done a lot of towing behind gas engines, and have been fine with them. Gas is sometimes easier to find, and right now anyway, very little price difference between gas and diesel. Living in the cold country, and I realize newer diesels have come a long ways, but you still have those cold morning start ups. Also, while I do a lot of long distance towing, I also use the same vehicle for a lot of around town driving. (And some long distance driving without towing.) But the gas mileage does make some difference, particularly with higher gas costs. (Right now, that's not to much of a problem, but I'm pretty sure we will see higher costs again.)
Foggy, your comments are exactly why I do not buy brand new cars anymore if I can help it. I've had very good luck with buying models that are 1-3 years old, under 35,000 miles, and that have been "lease backs" or dealer rental cars. At least that way I'm getting something that has been broken in, professionally maintained and already somewhere around 30% depreciated.
I hope to go look at a new Dodge 1500 Eco-Diesel this week. (As, there are no used one's listed.) Just to see one anyway, and give it due consideration. But as I look at everything, including my use of the vehicle, and with no future plans to tow anything bigger anytime soon, it may come back to just keeping what I have, or upgrading it to a newer model. I really have been quite impressed with the Highlander, and it has met all my expectationsl