Manufacturing Cost in Oil
I have seen some unsubstantiated assertions on blog discussions that the energy usage during automoblile manufacturing equals operational usage during the first 100,000 miles (on average). This number seems plausible but depresses many people as it prevents us from achieving a net high mpg -- say one that is beyond 20 MPG, if we include manufacturing influence.
Sanity checks on this assertion done a couple of different ways show that this amount would equate to 600,000 MJ of energy usage.
- Method 1: assume power consumption of 135 horsepower for 100,000 miles traveling at 60 mph gives 607,000 MJ
- Method 2: assume 20 MPG fuel consumption and 1 GJ/30 liter gasoline gives 630,000 MJ.
If anything, I find the assertion too bold. The Institute for Lifecycle Energy Analysis has done this study and determine the actual numbers, which are less than 1/5 the assertion. So in actuality, the mileage cut-off is closer to 20,000 miles of driving when we match the sunk energy costs of manufacturing for a typical vehicle.
check the chart out:
Conversion factors obtained from the useful Standards Measures web site.
Added: Fixed GJ/liter conversion factor type