The drivetrain was the standard 2.4-litre diesel and six-speed manual permanent four-wheel-drive transmission.

Hybrids are also known for averaging more miles between road calls than standard diesels.

The fuel produces 78 percent less carbon-dioxide emissions than standard diesel.

Should the system malfunction it reverts to the standard diesel mapped ignition, thus offering the same reliability as the production car.

And its fuel consumption was 11.6 miles per gallon, as against 8.6 for a a current hybrid and 5.8 for a standard diesel under similar test conditions.

Instead of standard diesel, they use fuel similar to that used in jet airplanes.

Biodiesel has fewer emissions than standard diesel, is biodegradable, and is a renewable source of energy.

In other words, it takes about 1.1 gallons of biodiesel to equal 1 gallon of standard diesel.

The buses provide approximately 40% better fuel economy but cost about two and a half times more than a standard diesel bus ($210,000 versus $80,000).

Biodiesel is also safer to handle and transport because it ignites at a much higher temperature than standard diesel or gasoline.