So it is great that several cars now claim to have over 100 mpg combined miles per gallon equivalents - but there are a few caveats to this news. These are all electric vehicles, and thus benefit from the conversion factor set out by the EPA for equivalent “fuel” costs of electricity. This is the “black box” number. Aside from the immediate pocketbook concerns, there is an underlying concern with fuel consumption and the related reduction in C02 output. So there is no way to average electric power, since regional sources will greatly affect this C02 count – from hydroelectric to coal, for example. There is also an issue of the batteries, which not only are costly, but represent related CO2 costs in production. I’m not against electric cars, but would like to see true comparisons – for example, life cycle costs for the vehicle over 100,000 miles.
The other factor is a problem of mathematical representation. In the US, we present miles per gallon (distance per fuel quantity) – whereas in Europe, the variables are reversed and are presented as liters per 1,000 kilometers (i.e. fuel per a set distance). Why does this matter? Because the gallons savings are a diminishing curve to the increase in miles per gallon. For example, say you have a 20 mpg car, which takes 50 gallons per 1,000 miles and you want to upgrade. Increasing mpg by 10 to 30 mpg car brings you down to 33 gallons – a 34% improvement. Another 10 to 40 mpg is 25 gallons, but only a 24% improvement, and another 10 to 20 gallons, a 20% improvement. It is a diminishing return. Of course, all reductions in fuel consumption are good, but this type of accounting is increasing less relevant as we get into higher fuel efficiency vehicles.
Instead, a more transparent metric is the net quantity of fuel per a stated distance of miles. In the previous example, the choice would be a 33, 25, or 20. This is much more straightforward and easier to understand the relative improvement in fuel consumption. The chart of diminishing return also makes it clear that the “Cash for Clunkers” program was a very effective way of reducing CO2 output related to vehicles miles. Even if this program moved people from 10 mpg to 30 mpg, it saved 2/3 of the fuel costs for that vehicle, or 65 gallons per 1000 miles. It is a better measure of what we really are concerned with right now – which is fossil fuel related CO2 output.
So MAX was able to cover 1000 miles with 10 gallons of fuel. McCornack chose to use a diesel engine, both for the fuel efficiency and the versatility of fuel types, including biodiesel from fast-food cooking oil. And this is the real gem. It changes the economic dynamics of small scale biofuel production. The average miles driven by a car in the US is 15,000 (Federal standard) – of 150 gallons, or 10 – 15 gallons per month. Hmm… there is this Chinese place down the street that uses Soy Oil that they throw away every few days…..