Based on recent comments by Toyota executives, it looks as if the vehicle nobody thought would happen might. Recently, the whole green car battle has been between hybrid and clean diesel advocates. Each claiming the technological and environmental superiority of the other. But now comes the possibility of the best of both worlds: A diesel hybrid.

Many claimed the cost of a modern diesel engine, on top of the cost and complexity of a full-hybrid system would make a diesel hybrid unfeasible for a moderately-priced mass-market car. But it doesn't seem to be discouraging Toyota. Simply changing out the Prius' current 1.5L gas engine for a similarly-sized turbodiesel could conceivably push the fuel economy figure close to 80 miles per gallon. Add plug-in capability on top of that, and you're looking at the possibility of the first mass-production vehicle that delivers an honest-to-goodness 100 miles per gallon. Assuming a 10-gallon fuel tank, you're looking at a  hypothetical range of nearly 1,000 miles.

I can already see this making major headlines across the U.S. and around the world. And don't think Toyota doesn't have the engineering might and marketing muscle to make it happen. Okay, so it probably won't go from 0-60 in four seconds flat. Ten seconds is more likely. But that seems plenty peppy for 100 mpg. Heck, most single-cylinder scooters don't get that.

I know the Prius is a polarizing vehicle, and I myself have railed against the smug aura of self-righteousness of many Prius drivers. But like it or not, building the first practical, mass-produced 100-mpg passenger car will be a significant technological achievement, especially if it sacrifices little in terms of passenger comfort, utility or value. Reaching this milestone, whichever manufacturer gets to it first, can ultimately only be a good thing.