Century of Progress
The above chart, which shows the negligible gains in fuel economy cars have seen over the last century (what efficiency gains there were have been plowed into horsepower and more weight), is from “Fuel efficiency of vehicles on US roads: 1923–2006,” by Michael Sivak and Omer Tsimhoni, published in the most recent issue of Energy Policy.
The authors note:
After the 1973 oil embargo, vehicle manufacturers achieved major improvements in the on-road fuel economy of vehicles. However, the slope of the improvement has decreased substantially since 1991. Specifically, from 1973 to 1991, the efficiency of the total fleet of vehicles has improved by 42% (from 11.9 to 16.9 mpg). This represents a compound rate of improvement of 2.0% per year. On the other hand, from 1991 to 2006, the efficiency has improved by only 1.8% (from 16.9 to 17.2 mpg), representing a compound rate of improvement of 0.1% per year.
The curve will begin to look dramatically different by the end of the second Obama administration.
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This entry was posted on Friday, May 29th, 2009 at 2:22 pm and is filed under Cars, Energy, Environmental factors, Gas prices. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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June 1st, 2009 at 6:52 pm
Rather optimistic are we?
June 2nd, 2009 at 10:36 am
I think a much cheaper and effective way to increase our efficiency and potential productivity would be an informational campaign to combat efforts to slow traffic and the popular misinformation on efficient driving habits.
We’d save much more fuel by improving the efficiency of our existing fleet than we will by attrition. And do it faster too.
Our population is getting old, slow, and lazy. What people need to remember is that slow does not equal efficient. (Fast can also be inefficient; when it’s sloppy and reckless.)
What Zero Growth Advocates don’t want you to know:
Faster acceleration is not significantly less efficient than slow acceleration. In fact, it’s generally more efficient, even before considering that it prevents, and speeds the clearing of, congestion and bottlenecks.
A car engine typically produces power most efficiently at about 3200RPM. It most efficiently delivers power to the road at about 2100RPM. But, more importantly, increasing the power delivered doesn’t decrease efficiency much until higher RPM, closer to 4000RPM. Gas consumption is actually lower at higher load and engine speed than at the low engine load and slow engine speed of gradual acceleration. (see Brake Specific Fuel Consumption)
Engines deliver power best at two spots. At low RPM and very light loads, such as for maintaining speed, and at higher RPM delivering larger loads, such as for more rapid acceleration.
And higher cruising speeds are actually more efficient up until aerodynamic factors dominate at about 55MPH . (see EPA Fuel Economy tips and MetroMPG.com post Speed kills: testing MPH vs. MPG in top gear )
Some observations that should put things into perspective: Driving increased pretty steadily until leveling off in about 2005. It peaked in Oct 2007, before prices spiked in spring 08. Despite the flat trend in driving, our fuel consumption continued to increase. You read that right. Fuel economy declined starting around 2005, despite our improving fleet fuel economy rating and no big increase in the amount cars on the roads (prior to then, fuel economy improved despite the great popularity of trucks and SUVs). Fuel economy didn’t rebound until the gas price spike in 08 drove poor, stupid and slow drivers off the roads (Sorry about the pun. I didn’t mean for it. Though I must admit, I like puns.)
So long as people believe slow is efficient, high gas prices will decrease our fuel efficiency and waste our time. (Except when lack of an economy leaves our roads empty and free flowing.)
What I’m suggesting is not aggressive driving. Aggressive driving is defined as rapid acceleration and braking. What I’m suggesting is that people should drive with ambition, with purpose and attention. By looking a head, drivers can make adjustments to speed using the accelerator pedal rather than the brake. With electronically controlled fuel injection, when cars are moving they can keep the engine turning with little or no fuel. It’s actually the braking that wastes fuel, not the rate of acceleration.
It’s not our desire for more power that has kept fuel economy from improving. It’s demanding more power, but failing to make use of it.
People need to act with purpose. It’s when we’re constrained from acting meanifully that ambition turns into agression or we turn to dangerous distractions like phone calls, texting, drinking, and day-dreaming.
Fat, slow, poor, and stupid is no way to go through life, it’s now way to run an economy, and it’s no way to prevent global warming.