I can tow myself along in traffic in my gas-fired car just by lifting the clutch, too.
It's not a function of available torque, but rather of the reluctance of the computer running the show to allow the engine to stall.
The diesel engine's management does this by increasing fuel, and the gasoline engine does it by increasing both air and fuel, but the end result to the user is the same: Pick an appropriate gear, ease out on the clutch, and the car goes forward.
Meanwhile: Here, diesel fuel costs more than gasoline. When I bought gas a couple of days ago diesel was at posted at $3.78 and gas at $3.12.
I'll leave it to you to make your own cost-per-mile comparison between your own turbo diesel minivan and a similar gas-powered model.
But just to pick an example, here's what I can glean from VW's American website:
Jetta TDI 2l turbo diesel: 42MPG highway
Jetta GLI 2l turbo gas: 33MPG highway
The TDI has more torque, the GLI has more horsepower. Peak torque is in about the same spot on the powerband. They both should behave similarly in normal road-going duties, and they both cost roughly the same to buy.
According to these numbers, the TDI costs $9.00 to go 100 miles down the highway, while the GLI costs $9.45. So the diesel is a bit cheaper, but not by much.
Things look slightly worse when comparing to a lesser engine, such as the perfectly-adequate 2-liter normally-aspirated gasoline 4-banger in the Jetta S, which burns $9.17 every 100 highway miles and costs $5k less than the TDI.
The diesel will go further on a tank of fuel, but then it might also have to go further because not every gas station here offers diesel.
So, yeah. Modern, small diesel engines are awesome little things -- there's no doubt about that. I'd love to have a TDI engine in something, just to tinker with and satisfy my hacker curiosity.
But in terms of saving money, where I stand? It's really not so clear-cut.