The Oil Drum

206 comments on DrumBeat: May 20, 2006

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GreyZone on May 21, 2006 - 12:55am

Vans, minivans, and SUVs are not horrible vehicles if you drive them with a full or nearly full passenger load all the time. But that's the problem - most people drive these monsters solo, with no one else in the entire vehicle.

Miles per gallon is not the only measure we should observe. We need to observe passenger miles per gallon. Yes, vehicles can and should get better mileage overall, but one SUV carrying 6 people and getting 12 miles per gallon is more energy efficient than 6 Camrys getting 40 miles per gallon being driven solo. Take a sample trip of 20 miles. The SUV will expend 1.67 gallons while the 6 Camries will expend 6 * 0.5 = 3.0 gallons for covering the same distance. This is precisely why mass transit is more energy efficient than solo drivers in cars. Even though something like a train gets far lower raw MPG, it carries far more passengers and/or cargo so the total energy expended is less per passenger or cargo pound moved.

If you drive your SUV with a full or nearly full load most of the time, then you are actually helping conserve energy. It's all those solo drivers, even in their hybrid Priuses that are wasting energy.

So carpool. It's a good way to start conserving energy. It's not the ultimate solution but it's a good place to start.

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Twilight on May 21, 2006 - 7:00am

I've been thinking about this lately, I've concluded that the only real measure is fuel used per unit time. It does not matter HOW you achieve it, the goal should be to reduce the number of gallons you use, say, in a month. If that be from a higher mpg car, or combining trips, or car pooling, or walking, or taking the train, whatever.

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louGrinzo on May 21, 2006 - 10:16am

Bingo! We have a winnah!

This is the point I keep making to people in person--don't get caught up in the minutiae of the situation, just look for ways to minimize your monthly energy expenses. Use less (turn off lights in unused rooms, batch errands together, car pool), and use energy more efficiently (use CFL's, drive with a lighter foot), and you can save a healthy percentage of your energy bill, beginning right now, without making a major investment or change in your lifestyle.

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Substrate on May 21, 2006 - 11:48am

Ah, but here's the tricky part of people miles per gallon:

Take an average four passenger Civic getting 32 miles per gallon. 4people X 32mpg = 128pmpg

And a large 7 passenger SUV getting 15 mpg. 7people X 15 mpg = 105pmpg

(For giggles you might also want to consider 5 people riding
in an Echo: 5people X 38mpg = 190pmpg)

First of all, with the (theoretical) vehicles at full
capacity the civic still beats out the SUV in people miles
per gallon. That could obviously flip if the SUV got better
mpg in this case, but it'd still be a close call.

Now the real problem...what's the likelyhood that you can
find 7 people all going in the same direction at the same
time? Pretty slim. How about four people going in the same
direction? Less slim, but still pretty slim I'd say. I'd
say that two people going in the same direction at the same
time is a lot more likely. So back to the math:

Civic: 2 people X 32mpg = 64pmpg
SUV: 2 people X 15mpg = 30pmpg

You somehow need to find twice as many people going in the
same direction to make the SUV match or exceed the efficiency of the smaller, better mileage car, and once you reach two people in the car (meaning four in the SUV) your likelyhood that all people are heading in the same direction at the same time decreases greatly.