Gas mileage

I cannot remember where I first read about this, but as it’s a fact I’ve enjoyed pointing out for years, I really enjoyed Brad Plumer’s post pointing out that automobile manufacturers have actually been churning out steadily more efficient engines.  The problem is that nearly all those gains have gone into more horsepower and heavier cars than into better mileage.  Optimistically, this means that if we actually focus on getting better mileage, this is pretty low-hanging fruit.  Somehow, I seem to survive just fine in my 116 hp Corolla.  Plumer:

The charts below, for instance, show how the Honda Accord has evolved over time. The car’s weight, horsepower and torque have all climbed dramatically since 1980. By contrast, the car’s gas mileage (shown in the lower right corner), spiked briefly in the early 1980s before plummeting and then largely stagnating for a decade:

Here’s another way of making the point: If Americans were still driving the same-sized cars that they were back in 1980, Knittel calculates, the average gas mileage of vehicles would be about 37 miles per gallon today, rather than the 23 miles per gallon we’re currently getting. But oil prices fell during the 1980s and 1990s, and fuel-economy standards stagnated. Automakers had few incentives to improve gas mileage. So they didn’t.

I do love how clearly those charts demonstrate the story.  I don’t really have anything to add, just think it is a fact that more people should appreciate and should definitely guide our policy regarding fuel efficiency standards.


About Steve Greene
Professor of Political Science at NC State

2 Responses to Gas mileage

  1. itchy says:

    I’m not sure this is the whole story. Yes, the same model of car grows over time. Just about every model — Camry, Corolla, Accord, Civic, Outback, 325, take your pick — all have gotten gradually larger over time. Look at a Camry from 1989, and it’s smaller than a Corolla today.

    But manufacturers have replaced these by sliding lower-end models into their lineups. So the Tercel of 2000 was similar in size to the Corolla of 1990.

    I think the idea is to get you hooked on a model, then gradually step you up as you repurchase that same model. It’s not just the size and horsepower that increases, it’s also the cost and, probably, profit margin.

    Another explanation is that it’s not an intentional plan, it’s a natural arms race between similar competing models. If the Accord adds a little something, the Camry has to add something, too. Gradually, they become bigger, faster, more comfortable. These are easy things to add to get that slight advantage when Consumer Reports compares your cars for the new year.

    You can see similar unintentional effects in software and other industries.

    But I agree that even the new low-end models do not get better mileage than the cars they replaced. Most of today’s cars don’t get better gas mileage than 25 years ago.

    In 1987, I bought a Honda CR-X. I got the sporty model that got 36 mpg, but there was an HF (high fuel-efficiency?) model that got 51 mpg. Not a hybrid, just a regular engine that didn’t stop idling when you sat. Today, people pay a premium for a Prius; this car was the cheapest in the lineup.

    And I remember a commercial in 1977 for the Mazda GLC that got 35/45 mpg.

    On the other hand, I’d bet if I sat in that GLC after sitting in a 2012 Mazda 2 (sorry, Mazda, I actually had to look that up), I’d notice a big difference. Even at a similar size, I suspect today’s cars are far more luxurious with maybe many more gadgets (and safety features?) and such that add weight and use power, etc.

  2. Alex says:

    A couple comments:

    1) A big reason cars have gotten bigger and heavier is safety features: air bags, crumple zones, and a whole host of much smaller things (sensors, actuators, etc.) all add weight and volume. (This is a big reason, but it’s certainly not the only reason.)

    2) Cars, while not getting better MPG, have gotten cleaner. In fact, a great deal of the added under-the-hood complexity comes from emissions equipment. Sine the 80s, cars have gotten better at reducing tailpipe emissions, but that doesn’t mean they’re better at using less gas per mile.

    I think it’s true that the public and the car manufacturers haven’t done enough to raise mileage standards over the years. I just think the comment in the last chart — that we’d be getting 37 mpg instead of 23 if cars had stayed the same size — is inapposite. Cars can’t have stayed the same size to get the safety and efficiency and comfort we demand today; but manufacturers would have devoted more resources and given us more efficient cars by now.

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