Let’s take a quick look at the composition of the 2004 fleet -- all the 2004 light duty vehicles sold in the US that have an EPA mileage rating. “Heavy-duty” vehicles do not receive a mileage rating. This excludes certain passenger vehicles such as the Hummer, higher end pickups and so on.

Still, there are 1,964 model configurations of model year 2004 light-duty vehicles, import and domestic, offered in the US.

Each has an EPA mileage rating consisting of City and Highway. Plotting that data results in the cart on the right. (Click on the image to enlarge.)

The height represents the number of model types for a given combination of city and highway mileage. You’ll see that although there are a very few outliers on the ultra-high and ultra-low fuel efficiency ends, that the majority of model types cluster between approximately 20-35 mpg.

Here’s another way to look at this. The chart on the left plots the combined mileage rating for each of those 1,964 vehicles by putting them in different bins. (Click on the image to enlarge.) Again, you see that the bulk of models cluster in that middle sector.

This makes sense when you consider that the Federal government’s CAFE standards mandate an average for the fleet (by manufacturer).

What is also interesting is taking a look at how each manufacturer then compares to each other. I’ve done another plot, this one taking all the models offered by GM, Ford, DaimlerChrysler, Honda and Toyota. (The old Detroit Big 3 and the most fuel-efficient imports).

To try to keep the plot easier to interpret, I used columns to represent the Big3 and lines to represent Honda and Toyota. (Click on image to enlarge.)

One thing you see immediately is that the distribution patterns of the Honda and Toyota fleets shift to the right toward more fuel efficient vehicles. That does not mean that these two automakers don’t offer their own guzzlers. The chart also highlights that all the auto manufacturers have the majority of their offerings in the mid fuel-efficiency range. But the chart also highlights the emerging difference on the most fuel-efficient end of the scale -- which is partly due to the hybrid models offered by those two.

All that said -- these charts just represent what is available, NOT the ultimate fuel-efficiency of the 2004 fleet as represented by the numbers of vehicles people buy. I am going to try to come up with some more specific purchase data for 2003 or the first quarter of 2004 to put a visual image on the reality as well as the potential.