The other day, a remodeling contractor was working at the next-door neighbors' house and I eyeballed the two trucks that he sent his workers and supplies in.

One was an older Mercedes-made Sprinter cab-chassis truck with a box body, and the other was a near-new Nissan Van, an NV-2500 with a high roof.

Here was a study in engine applications, that is, gasoline vs. diesel. Each of the trucks sat for a couple of hours before running off to fetch more supplies. Then they sat for several more hours.

"That's an application for gasoline," I told my wife. She answered, "Hmm?"

But I warmed to the subject. "Really. The trucks are just sitting there. Gasoline makes a lot more sense for something like that."

"Oh. Yes," she said.

The rest stayed in my head: While in motion, the Sprinter's five-cylinder turbodiesel saves quite a bit of fuel, because in mpg terms, Sprinters get into the 20s. But while sitting in the neighbors' driveway, the diesel saved nothing, while its owner, the contractor, was probably still making payments on it because it probably cost about $35,000 to buy.

The NV's gasoline V-6 or V-8 uses more fuel while going down the street, maybe getting 13 to 15 mpg. But every minute it sat around, it was justifying its purchase cost of maybe $27,000 - thousands less than any diesel. I could understand why the contractor chose the Nissan Van, which comes only with gasoline engines, over another diesel Sprinter.

Don't get me wrong. A diesel-powered Sprinter's good fuel economy makes it great for high-mileage applications. But if the job next door is typical of how this remodeler uses his trucks, the Sprinter was surely taking a long time to pay off its higher upfront cost.

Any diesel-powered light or light-medium truck, no matter who makes it, needs high annual miles to justify its $5,000 to $8,000 price premium over a gasoline-powered version. You've got to run at least 25,000 miles a year to make a diesel worthwhile. In other words, you can buy a lot of gas for five or seven or eight grand.

That's especially true today, because gasoline here in central Ohio has just dipped several cents below $3 per gallon -- $2.979 at stations nearby -- while diesel fuel is about $3.879. That makes gasoline seem even smarter. Certainly fuel prices will change soon, and maybe drastically. But since 2008, diesel has stayed higher than gasoline, and sometimes substantially higher.

The heaviest truck you can buy a gasoline engine in is currently Ford's F-650 with the new Triton V-10 option, which costs about $8,300 less than an F-650 with a Cummins ISB, the only other engine offered. That makes me wonder when more builders will offer gasoline engines in heavier trucks.

And I'm gonna look for more driveways with more trucks.