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Study Assesses Product Attribute Trade-offs and Technological Progress; Meeting Proposed Obama Fuel Economy Standards Will Require Downsizing and Change in Fleet Mix

Changes in the attributes (clockwise from upper left, weight, power, fuel economy and torque) of the Honda Accord over time as an example of fleet trends in the US. Knittel, 2009. Click to enlarge.

Based on detailed model-level data for US light-duty vehicles from 1980 to 2006, a recent analysis by a UC Davis researcher found that if weight, horsepower and torque had been held at their 1980 levels, fuel economy for both passenger cars and light trucks could have increased by nearly 50% from 1980 to 2006. In contrast, fuel economy actually increased by 15% during that period.

Christopher Knittel, of the UC Davis Department of Economics and Institute of Transportation Studies, developed a model to examine the technical relationship between vehicle weight, engine power and fuel economy—to which he refers as a production possibilities frontier (PPF)—and how this PPF shifts out over time. As part of the study, Knittel also investigated the relative efficiencies of manufacturers. He found that:

  • US manufacturers tend to be above the median in terms of their passenger vehicle fuel efficiency conditional on weight and engine power, and are among the top for light duty trucks;
  • Honda is the most efficient manufacturer for passenger cars, followed sequentially by Toyota, GM and Nissan.
  • Volvo is the most efficient manufacturer of light duty trucks, followed by Subaru, GM and Honda.
  • Over time, US manufacturers’ relative efficiency in both passenger cars and light trucks has degraded.

Next I compare firm-level efficiency across passenger cars and light duty trucks...ranked by the light truck fixed effect. The estimates are ranked by the firms’ light truck efficiency; the rankings change considerably. Honda, Toyota and Nissan rank higher than US manufacturers for passenger cars (Nissan and GMC are effectively equal), but the three Japanese manufacturers trail GMC when building light duty trucks, while only Honda surpasses Ford. At a first glance, these results suggest that the decision of US manufacturers to focus on light truck sales may have been a good one. However, a further cut of the data suggests that this is not the case.

...While across the entire sample, GMC and Ford are among the best in terms of fuel efficiency, over time their relative positions have diminished. Firms such as Audi, Toyota, Honda and Subaru have made large gains relative to US manufacturers. Across all manufacturers, 86 percent of the firms increase their relative position compared to Ford; all of the firms increased their position relative to GMC, while 43 percent did so relative to Chrysler.

—Knittel, 2009

The study also found that once technological progress is considered, meeting the CAFE standards adopted in 2007 under the Bush Administration would have required halting the observed increases in weight and engine power characteristics, but little more. In contrast, the standards recently announced by the Obama Administration, while attainable, require downsizing and a shift in the fleet mix away from SUVs.

Unlike the weaker Bush standards, the Obama standards will require moderate “downsizing” of vehicle characteristics—either shifts to more passenger cars or reducing weight and engine power characteristics near their 1980 levels. With average technological progress for cars and trucks and no shifting of the car/truck mix, we can only meet the standards with weight and engine power levels equal to their 1980 levels; changing only the car/truck mix does not achieve the standard. More rapid technological progress makes the standards easier to achieve, but still requires changes in fleet characteristics, either through the car/truck mix or weight and engine size.

—Knittel, 2009.




WOW. What insight – SUVs are less fuel efficient than mid sized autos regardless of who makes them.

This reads like statistics looking for a conclusion.
I think the conclusion is foregone and simple.

Lighter vehicles and lower horsepower are the main drivers of reducing fuel consumption. Technology, by itself, can provide only evolutionary reductions (if we are talking about ICEs, not EVs.)

I question the inclusion of torque. I would think torque from large displacement adds weight (which is already covered) and turbocharging is covered by horsepower - and the plots do not reflect torque as a driver.
Do higher rpm engines have significantly better SFC? Maybe so.

And the assumption that this is impartial is not helped when it comes from California - UC Davis Department of Economics and Institute of Transportation Studies.


It is most unfortunate, that, to satisfy an ill-advised acquired attribute in USA and Canada, too many vehicle manufacturers progressively inflated their products during many decades.


It is most unfortunate that, for decades, too many buyers purchased larger-than-needed vehicles.

Plenty of excellent medium and small cars have been available for almost 40 years but they are still only slowly increasing their market share;
and "small", inefficient SUVs are still selling well.


The Union of Concerned Scientists designed a Ford Explorer that got over 30 mpg and performed about the same as the one that got only 15 mpg. This is something that we could do, but chose not to. It is a bit of a failing in what we call "freedom". The freedom to drive a gas guzzler, that uses twice the fuel and causes others to go to war to fill your tank is not freedom for all.

The Goracle

Meeting Proposed Obama Fuel Economy Standards Will Require Downsizing

So more people will die. WHO CARES?!?!?!?! In order to appease the god of Globalwarmism we will sacrifice our children on her altar! Praise be to Algore. Praise be to Algore! Drive small cars or the god of Globalwarmism will be ANGRY!!!


Where are the eco freaks who want to tax fuel at $5.00 per gallon and tax parking spaces provided by employers for their employees.

Let's hear from you.

All together now children you must all drive bicycles.


The war in iraq is not being fought over oil but to keep the Zionists in Tel Aviv happy.


It is freedom of choice to drive a gas guzzler.

Is was government (apparently driven by voters) choice to go to war.

It is government (apparently driven by voters) choice to allow gas guzzlers to remain affordable.

Apparently all the worlds car makers know that a 30 MPG mid sized SUV (with the compromises required) would NOT sell.


Um, guys? The chart shows that the same model of car over 25 years got 50% heavier, and twice as powerful. To be fair, the Honda Accord from the 1980's was probably rightfully considered a compact car, and the civic used to be a subcompact. They both went up a size class, because that's what Honda thought best for the brand, and it sold pretty well.

So...this is not a strict analysis of what would happen to a midsize or compact car today if you tried to put the most fuel efficient 75 hp motor today into a 2200 pound compact car. Have motorist expectations changed in 25 years? Yep. Could they change again? Sure.

Remember the 1960's when Detroit had to make oversized, over-powered cars to appeal to "the buyer," except it turned out it was mostly to push the higher margin features, because the labor costs were about the same on small and large cars? That was the 1990's too. SUV's were already passe before oil hit $140/barrel last year.

Drivers don't necessarily want tons of horsepower, but the do want torque. Sounds like a hybrid or an electric would do. Drivers don't necessarily want a massive vehicle, but they kind of like the idea of safety. 6 airbags, ABS, and decent bumpers pretty much get your there...which smaller cars are starting to come with standard.


Drivers want enough horsepower to accelerate adequately (0 to 60 in 12 to 15 seconds) with maybe a little extra for ego.
Torque does not make a car accelerate to highway speeds, horsepower does. Torque (hp at low rpm) makes a car seem to accelerate effortlessly (quietly).
Most hybrids and electrics have plenty of quiet horsepower.

SUV/truck buyers usually want a roomy vehicle.
Contrary to what I see here, I believe many/most pickups and SUVs are about utility and safety.

Crew cab pickups and 7 or 8 passenger SUVs with room for kids, lawn chairs, sports equipment and coolers.

I don't expect the EV1 or Insight I to return.

Will S

The IEA has discovered that what they thought was a pessimistic finding in 2007 that oil fields were declining by 3.7% has really proven to be 6.7%;

Forget "adequate acceleration", there will not be adequate oil supplies for people to proudly display their status with large, ungainly gashogs that raise the collision mortality rate of families with more responsible choices just so the gashogs can carry around unfolded lawn chairs. The future will have a very different normal that many people will have a hard to becoming accustomed to.

The EV1 or Insight I will likely not return, but we've seen that many other vehicles with similar or better energy efficiency (unless one has had their eyes closed to the other articles on this website).

Will S

(forgot to close an HTML bracket above)

The IEA has discovered that what they thought was a pessimistic finding in 2007 that oil fields were declining by 3.7% has really proven to be 6.7%;

IEA Lead Economist Warns about World Oil Supply

Forget "adequate acceleration", there will not be adequate oil supplies for people to proudly display their status with large, ungainly gashogs that raise the collision mortality rate of families with more responsible choices just so the gashogs can carry around unfolded lawn chairs. The future will have a very different normal that many people will have a hard to becoming accustomed to.

The EV1 or Insight I will likely not return, but we've seen that many other vehicles with similar or better energy efficiency (unless one has had their eyes closed to the other articles on this website).


For those who think they need an appartment size vehicle for weekends and to drive the overweight family members around, there are many very large size recreational vehicles for sale at a good price.

Alternatively, they could use their 70+ft house-trailer on 18+ wheels, 750+ hp, 200+ gals/tank (with the large boat attached) to drive up and down the street to impress their neighbours.

Of course two Prius III could also move the average large family around but that would be less impressive.

We do have a huge attitude problem to solve.


Forget attitude modification.

Our problem is that gas that is cheap in dollars but expensive to our near and far future.


Status can be a matter of audience. If the general impression that gas guzzling is anti social, then there will be no positive status, only negative. The person seeking status needs and audience to be impressed, if that audience is reviled, then there is no gain to the ego.


I can't think of anything that was on the road in 1980 that I'd want to drive today. But...if we're to go back to 1980 specs to save the world, do we also get to go back to 1980 emissions and safety regulations as well?

Or are we supposed to have our cake and drive it, too?


@ Mathew,

The safety and emissions specs changes since 1980 (in California, anyway) only need add a couple hundred pounds to the vehicle. Meanwhile, many other components have gotten lighter, cleaner, more hp per liter of displacement, and more efficient at wringing power out of fuel. Smaller engines can offset some the weight.

I don't know if this statistic is still valid, but some years ago researchers claimed that if every American just drove the most fuel efficient version of the make and model they already drove (the 4 cylinder instead of the v-6; the v-6 instead of the v-8), that the US would save something like 2 million barrels of oil per day. All the safety and emissions gear, cargo and passenger spaces would be exactly the same.

My only complaint about Cash-for-Clunkers is that they should have required more than a 4 mpg improvement to receive the incentive.


The Rockie Mountain Institute ( showed that a lighter car is a more fuel efficient car. If you use carbon fiber, it can be a stronger and safer car as well.

Stan Peterson

Have we yet heard from all the new Puritans of the great anchronistic Druid Nature Worsahippers? Hurry up then,and post. As far as a car being adequate with a 0-60 of 15 seconds, I recomend you drive that death trap and I welcome your Darwin award as you achieve your aims in reducing the pressure on resources by a human, in a vaib attempt to merge safely on to a freeway.

Really I look forward to the coming days in a decade or two, when I can have my cake and eat it too.

Only you nouveau GOREan Puritans believe that small cars are what the majority want, in any country. It is merely the compromise that they were forced to accept; and will be abandoned readily everywhere, when fuel and wealth are in greater supply. When Electric Drive substitutes arrive, they will improve and grow in size and comfort.

I expect that the only free vote on car size occurred in the USA in the 50s and 60s, when fuel costs and emission concerns were not a consideration at all.

We have met all the genuine toxic emsissions even on the ICE, and energy will soon return to a commodity NOT in short supply, when we transition from fossil to fission and fusion.

Will S

"Status can be a matter of audience. ... if that audience is reviled, then there is no gain to the ego."

Some of the 34% of Faux News watchers would gleefully drive an SUV just to dismay those who give a ___ about their kids future on this planet. And they would also drive them to be seen and admired by their fellow 34% FN watchers.

Indeed, Faux News tries to establish those who are responsible with their vehicles as the villains who should be despised.

Fox News: Green With Envy - Prius Owners Smile as Neighbors Fume


America is still a democracy (of sorts) so if 34% want gas guzzlers and 66% want clean fuel efficient vehicles, then we can make progress. Lots of people think it is their right and freedom to drive a big SUV and have a huge motor home in storage. Those are probably the same people that have "Support Our Troops" bumper stickers.

Will S

Sadly ironic that the troops are fighting an oil war the SUV drivers are contributing significantly to. Outward shows such as having a bumper sticker has never impressed me. Actions speak louder than words, and those who don't want to send our troops overseas to fight in oil wars should do everything they can to reduce America's dependence on foreign oil. It'd be even sadder if those SUV drivers felt that "freedom" meant driving an SUV while having a perceived dispensation by having a "Support the troops" bumper sticker.

A better bumper sticker would read "Support the troops: cut your oil consumption"

Henry Gibson

Just look at the announcements of new car engines on this site. XX more horse-power YY more torque. The full electric cars are 0 to 60 in less than XX seconds 100 plus horsepower.

Yes merging lanes on freeways were designed for danger, but that is no excuse for over-powered cars that sit in the garage or driveway most of the week or even cars that are used to commute every day. Hydraulic hybrid cars can be designed to give all of the acceleration needed. Diesel locomotives proved the versatility of the hybrid drive over eighty years ago.

If every California and Washington DC area car were required to have the ability to creep in traffic jams with electric power or hydraulic power with the engine turned off the the efficiency of that section of the freeway would multiply and the air clean up. It takes less than a horse-power to creep on a freeway even up some fairly steep grades. The engineers and scientists can quicky find that a horsepower is 550 foot pounds per second, and if your car weighs 2200 pounds, a long ton or about a tonne, your car could be pulled vertically into the air at fifteen feet a minute with one horsepower. One horsepower should enable a big car to go 5 to 15 miles an hour on a level freeway with no wind.

CALCARS, Electric car people estimate less than 200 watt hours per mile for average driving. This means that one horsepower is good for nearly four miles an hour in such cars on the average. The battery will allow much faster peak speeds. ..HG..


200 watt hours takes my electric bike 8 miles at 8 miles per hour. I can get around most places I want to go and recharge in 3-4 hours. Lots of people would say that they could not use an electric bike and maybe not, but they sure are a lot of fun and do not cost much.



How fast does it go if you pedal and use the electric assist? I've ridden a segueway at almost 12 miles per hour, and that felt awkwardly fast, but a 10-speed at 15 miles per hour seems pretty controllable?

Do you get about an hour of boost?

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