MPG estimates are NOT linear: please replace your SUV now

June 20, 2008

NPR did an interesting report about bad MPG analysis based on research from a Duke Professor (my alma mater) . The crux of the report is that small MPG improvements (e.g. +5 MPG) at the bottom have a much bigger impact on actual fuel used ($$$) than the same improvement at the top. So replacing a 30 MPG car with a 35 MPG car is a much smaller real consumption difference than replacing a 15 MPG one for 20 MPG.

This is not surprising. If fact, it’s painfully obvious if you present the data as a percentage (33% vs 17%) but we’ve gotten so used to looking at the just the MPG #s.

(sourc: http://www.dotnetcharting.com/)
So, take everything back to $ for your estimations and you’ll be fine. That same analysis may point you away from a hybrid into a small ICE. But now we’re assuming that you can make a logic based decision about buying a car. Most of the research out there says that car buying is a emotional decision for most of us.

Note: cross posted to RAVolt.com



  1. In Canada we measure Liters per Kilometer not miles per gallon. Besides the obvious conversion to metric it’s the fact that it’s liquid over distance that’s really different. I’m starting to think it might be a better way to compare mileage.


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