For Earth Day 2006, AutoWeek magazine ran an interesting test. They got a bunch of people together and took a 349 mile drive. The destination was Lake Michigan for some Red Tulip Ale. In 1990 they ran a story on future technologies that would change driving for the greener, so they decided to try some of them out, sixteen years later. They took five vehicles:

  • Chevrolet Corvette. EPA highway rated at 27 mpg. Come on, AutoWeek is a car magazine. Do you really think they wouldn’t take some fun cars along, just because?
  • Honda Accord V6 hybrid. EPA highway rated at 34 mpg. Sure it’s a hybrid, but its more performance oriented.
  • Jeep Commander. EPA highway rated at 18 mpg. A 5000 lb V8 seven passenger SUV. They brought this to carry all the camera equipment. I like that they took the extra step of running the numbers on it as well. It serves as an interesting control.
  • Toyota Prius. EPA highway rated at 51 mpg. The standard-bearer for hybrid efficiency.
  • Volkswagen Jetta TDI. EPA highway rated at 42 mpg. You knew I was interested in this story for a reason, right?

The mileage numbers they measured worked out this way, in ascending order:

  • Jeep Commander: 17.2 mpg (0.8 mpg worse than EPA rating)
  • Chevrolet Corvette: 27.3 mpg (0.3 mpg better than EPA rating)
  • Honda Accord V6 hybrid: 33.9 mpg (0.1 mpg worse than EPA rating)
  • Toyota Prius: 42 mpg (9 mpg worse than EPA rating)
  • Volkswagen Jetta TDI: 49.9 mpg (7.9 mpg better than EPA rating)

It’ll be interesting to see what happens with the EPA ratings when they change the test regimen to reflect today’s driving. The three poorest performers were within 1 mpg of their EPA rating. Certainly the hybrid numbers will suffer, but the new ratings should be more accurate. The biggest surprise to me is the Corvette. It was only 6.6 mpg less efficient than the Accord Hybrid? With the Corvette’s V8 capable of delivering 400 HP, this is no small feat.

Also, it’s important to note that the AutoWeek comparison was not a controlled test. They gathered a bunch of people into a bunch of cars and drove in a group, to the lake and back. Take from it what you will.

This said, my favourite part of the report is:

Our fuel station was offering up B20 biodiesel, 20 percent of which comes from vegetable oil, animal fats and other sources, meaning that from an environmentalist’s perspective the German diesel didn’t just beat the Japanese hybrids, it trounced them. Not only that, it had more than half of its 14.5‑gallon tank left at the end — it could have made the same trip again without refuelling!

The author goes on to wonder what a small turbo-diesel mated to an electric motor could do. It seems an ideal match given the efficiencies involved, but I’ve seen it suggested that it wouldn’t work as well as one might expect. Both the diesel and electric engines excel at low-end torque, while the gasoline engine delivers more as the revs go up. The gas and electric cover opposite ends of the range while the diesel and electric cover the same end of the range. I wonder if this would kill the advantages.