More on automotive fuel efficiency

EPA just released a big report on vehicle fuel mileage, summed up in this WonkBlog entry

A few comments:

A) I’m struck by how response fleet mileage seems to crude oil prices in their figure in point #1.  In 1979 you have a sharp spike in mileage that presumably corresponds with the Iran hostage crisis, and another steady rise over the last five years, a period of generally increasing oil prices with an all-time-high of ~$120/bbl in 2008.  So I’m optimistic that the industry will be able to meet the ambitious CAFE targets that they recently signed on to.

B) In the figure about increasing shares of advanced vehicle technologies (point #3), it’s worth noting that, except for the different transmission options and the direct injection vs. diesel, none of those categories are exclusive. For example, my buddy’s late model Toyota Prius covers at least 5 of the categories (variable value timing, multi-valve engine, cylinder deactivation, hybridization, and a continuously variable transmission).  This becomes very interesting when you look at the increase in fleet mileage (point #5) by the nationality of the manufacturer:Mileage

My impression is that the highest-mileage models available from the Japanese manufacturers feature advanced hybrid technology, while the German manufacturers have focused instead on high-efficiency diesel designs (though that is starting to change).  In the future I expect we’ll see more models that marry these two technologies for maximum fuel economy performance, e.g. like this and this (go VW!).

C) The Rocky Mountain Institute has placed vehicle weight reduction at the core of the vehicle mileage technologies it touts in the context of its Hypercar concept.  However, real-world improvements in this area in the last 10 years have been limited to stopping the increase in vehicle weight over time.  This is a key area for improvement in the future, though it is also very challenging in the context of switching over to hybrid- and fully-electric vehicles with low specific energy storage batteries, as well as the arms race mentality of vehicle safety.

D) There’s nothing at all in the post about biofuels, and the original EPA report only makes a few passing references to flex-fuel vehicles (in the context of very few people actually running E85 in them!).  But I have to point out that, if you take these vehicle mileage increase trends an superimpose a 50% or 60% GHG reduction (advanced and cellulosic fuels in the RFS2, respectively) for 1/3 of all fuel consumption in the US, the total GHG footprint of transport in the US starts to look a lot better.

Taken all together, there’s a lot of reason for optimism that the US will be able to make some significant gains in vehicle mileage after decades of stagnation, and actually realize the associated mitigation wedge.

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