New Gas Mileage Rules Will Reshape What Americans Drive: Engines And Transmissions

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VW logo and sign at opening of Volkswagen engine plant in Silao, Mexico

VW logo and sign at opening of Volkswagen engine plant in Silao, Mexico

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Smaller, more efficient engines better matched to more complex transmissions will have some of the biggest effects in making tomorrow's cars more fuel-efficient.

The 2025 corporate average fuel economy (CAFE) level of 54.5 mpg translates to about 42 mpg on the EPA window sticker.

And while Toyota Prius hybrid owners may note that they can do better than that today, the average applies to all vehicle types--not just small cars but even full-size pickup trucks.

Reduced weight and lower wind resistance will play a role in getting your next vehicle to deliver better gas mileage than ever before, no matter how large or small they are.

And many of the changes will come in engines and transmissions.

This is the second of three articles on the future technologies that will boost fuel efficiency in future cars.

So what will those changes consist of?


Engine efficiency improvements may be the single biggest factor in improving gas-mileage ratings for the next few years.

A variety of technologies--direct injection, variable valve timing and valve lift, even electrically actuated valves--are already making combustion more efficient.

That permits what's known as "downsizing": an engine, frequently with fewer cylinders, that's smaller, lighter, and has fewer moving parts--which reduces fuel-wasting internal friction.

To make up for fewer cylinders, many of these engines are turbocharged--using otherwise wasted exhaust heat to power a pump that packs more air into the cylinder.

The resulting higher air pressure can be combined with more gasoline, meaning the engine produces more power on combustion.

That gives these engines higher horsepower for their size than "regularly aspirated" engines, meaning a four can perform like the V-6 it replaces.

In other words: Don't count the gasoline engine out for many years to come.

2011 Ford F-150 EcoBoost rear view - Drive Tour 2011

2011 Ford F-150 EcoBoost rear view - Drive Tour 2011

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Example: EcoBoost

The best example of this is Ford's line of EcoBoost engines, which started with a 3.5-liter turbocharged V-6 with the same power and towing capacity as the larger V-8 it replaced in Ford's best-selling F-150 pickup truck.

That engine has been a surprise, selling much better than Ford expected, especially in full-size pickup trucks.

It was joined by a 2.0-liter four that replaces a 3.0- to 3.5-liter V-6, and then by both 1.5- and 1.6-liter fours that replace larger standard 2.5-liter fours.

Most recently, Ford has added a 1.0-liter three-cylinder turbocharged engine, which replaces a conventional four of up to 1.6 liters.

And, who knows, there may be more to come.

The downside of smaller turbo engines is that they're more economical under light load than the bigger ones they replace, but equally thirsty at high power.

So aggressive drivers may find them thirstier than their EPA ratings, while gentler souls do just fine.

Few V-8s outside trucks

By 1970 or so, even so-called compact sedans offered V-8 engines. The only sixes were on base models, and four-cylinder engines from U.S. makers were a rarity.

2011 Hyundai Sonata 2.0T

2011 Hyundai Sonata 2.0T

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The rapid market gains achieved by smaller, more fuel-efficient, and better-built Japanese cars taught Detroit a 20-year lesson.

Now, if anything, some categories of U.S. cars use smaller engines than their Japanese competitors.

Big V-8s these days are limited to full-size pickup trucks--all of which come with V-6es as the base engine now--and a handful of pony cars and high-end large sedans.

The V-6 has effectively taken the place of the V-8, but it's really four-cylinder engines that are now the norm.

Andthey can be much larger than the 1.2- to 1.6-liter "econobox" engines that some buyers still imagine them to be.

Fours are the default

Around 2010, makers began to get rid of their V-6 options in both mid-size cars and compact crossovers, and the trend has accelerated rapidly.

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Comments (13)
  1. "Performance has increased fairly steadily over the last 20 to 30 years; you might be shocked at how slow even a more powerful car from 1993 actually is. Today's compacts are often capable of out-accelerating full-size sedans from the 1980s." And later, "...But their acceleration from, say, 60 to 80 mph was more anemic than it would have been with a larger engine."

    Were cars from 20-30 years ago unsafe *because* of their lesser power? Is accelerating anemically from 60 to 75 mph unsafe? Pushing 80 is unsafe on all but a few roads anyhow. Are our lives that much better because of these decades of performance improvements? I'm fine with a '93 Civic (with its better visibility (safety!) than today's cars and add today's crash safety.

  2. @Gene: First, when all cars are slower, differences in acceleration & speed that lead to driver impatience or road rage are reduced.

    Second, for trained drivers concentrating on the task at hand--not their devices, stereos, meal, or makeup--it's not at all unsafe to drive "pushing 80". U.S. Interstate Highways were designed to let cars of the FIFTIES travel safely at speeds of 80 mph. Today's cars have far better brakes, suspension, traction & roadholding.

    I'd argue it's U.S. drivers and appallingly lax licensing standards that make our roads "unsafe," if in fact they are:

  3. @John: Thanks for your reply. How often have you found yourself driving 60mph and thought, "I need to speed up to 80, and quickly!" If there's dense enough traffic to be worried about adjusting quickly to it, I'm surprised you think 80 is reasonable; human response times (moving the foot from accelerator to brake) are limited (and haven't improved) despite all the new technology to help the car respond better to the human input. Many a highway may be fine for 80mph without traffic, but why then care about getting to 80 quickly?

    No argument with your point about bad drivers making the roads even less safe.

  4. A truly good driver knows how to accelerate through a hazardous situation. In those cases, quick acceleration could be the difference between life and death.

    Also, performance of newer cars is not just about speed, but also handling and braking. Your '93 Civic is much less safe than a modern vehicle with proper handling and responsiveness. True, if you only drive below 35 mph, you will most likely be safe, but a '93 Civic is hardly comparable to today's cars.

  5. @Douglas: Thanks for your reply. It's sad that truly good drivers encounter hazardous situations so often, hopefully while driving to avoid such situations when possible.

    No doubt that new cars have performance improvements, particularly acceleration. Which did you want to emphasize as hardly comparable? I didn't quickly find '93, but did find '96:

    1996 vs. 2012 Honda Civic EX sedan:
    braking (60-0): 144 vs. 131 ft. (both have all ABS disc, as did '92-95)
    slalom: 62.7 vs. 64.6 mph
    lateral: 0.77 vs. 0.81 g's
    1/4 mile: 18.1 (75.3) vs. 16.9 sec (82.4 mph)
    0-60: 10.8 vs. 9.2 sec
    economy: 28/35 vs. 28/39 mpg
    weight: 2568 vs. 2741 lbs

    Maybe great advances came between '93 and '96, but says the '92-95 model was faster than '96.

  6. is the LAST PLACE I would trust.

    They are one of the MOST USELESS source of information since they don't disclose where they get those numbers from AND they don't test the cars.

    For all I Know, it could be some punk kids making up that site in their parent's garage.

  7. OK. Strike the second half of my last sentence then.

  8. "How often have you found yourself driving 60mph and thought, "I need to speed up to 80, and quickly!""

    All the time, almost every day!

    "If there's dense enough traffic to be worried about adjusting quickly to it, I'm surprised you think 80 is reasonable;"

    Say WHAT?!? Go drive in Germany; nominal speed on the highways is the equivalent of 140 MPH! How is it that no speed limits on the highways have worked for Germans for decades, but here we argue about 80 MPH as being unsafe?

    I am sorry we are even debating that, but I simply find it ridiculous.

  9. @Annatar: Your driving doesn't sound very defensive to me, but I guess I live in a sheltered world where I rarely have a need to drive above 75mph. I can certainly believe that driving 140mph would require a great deal of high end acceleration; I'm just crazy to find it unnecessary, unsafe when there's traffic, and not an improvement to my life.

  10. Sorry Gene, I tried to vote your comment up but hit the down by mistake!
    I like driving fast on race tracks and occasionally on the road, but I generally find the fuel inefficiency not worth the time savings these days. And safety is relative to the road and traffic conditions.

  11. High speed also reduces your tire mileage. If you like buying tires, drive faster.

  12. You must b

    Richard Franke shared a link.

    16 hours ago near Butler


    WHO"S ZOOMIN WHO ? Safty standards and Epa standards don't change the milage that much. But then how could they sell the "Hybrids" and make that extra $10,000 per car. If this honda got better milage. logged in to post your comment.

  13. I've been prodding media to read the EPA/NHTSA final rule and here's why: The EPA ran analysis on 47,000 technology packages for 19 separate vehicle types to determine which packages were most effective at reducing CO2 emissions. Copy/paste this link to see results.
    Wait for it to load the right page and then hover/scroll through the technology list. Legend for abbreviations is at the bottom of the chart.

    This GCC series covers some of these technologies, but completely removes the CO2 component of the story. Yet CO2 is a newer, larger and more powerful part of regulations that are transforming the cars we drive. It's big story that consumers need to know.

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