It’s official: Cars in the U.S. are more efficient than they’ve ever been. The average vehicle bought last year covered 23.6 miles on a gallon, up from 22.4 miles the year earlier, according to a new report (PDF) from the U.S. Environmental Protection Agency. Automakers are on track to hit a fleetwide average of almost 55 miles per gallon by 2025.
Many of the gains have been driven by electric technology—better batteries and magical systems that recharge them when a driver steps on the brake—but old-fashioned engines that run on dead dinosaurs are moving the needle, too. Almost 700,000 Americans (PDF) are tooling around in new Ford (F) F-series pickups this year, the base model of which gets slightly more than 20 miles per gallon on the highway.
How are engineering wizards getting to mileage numbers like that? We took a look under the hood and talked to the folks at the EPA to find out. Here are four technical terms that make a difference and what they mean in layman’s terms:
1) Direct Injection (31% of new cars) Engine efficiency surged when carburetors were replaced by fuel injectors. Now several new engines come with systems that shoot gas directly into each cylinder, as opposed to mixing it with air outside and having a piston “pull” the explosive soup inside the combustion chamber. In the end, the whole process is more precise and the engine can dole out less gas.
2) Cylinder Deactivation (8% of new cars) Why choose between a V8 and a V6 when you can have both? When a big engine idles, or cruises, its cylinders are almost starved for air. They aren’t using much gas, but the gas they are using isn’t being burned very efficiently. A growing number of vehicles—typically larger trucks—now have systems that idle two cylinders when the driver is cruising, routing the same amount of air to fewer combustion chambers.
3) Continuously Variable Transmissions (15% of new cars) Drivers tend to burn the most gas, by and large, right before and right after the car is shifted up to a higher gear. A variable transmission, however, functions sort of like a belt around two pulleys that are constantly shifting in size. Since there aren’t gear levels per se, the vehicle always stays in the efficiency sweet spot. (Here’s a nice animation of what it looks like.)
4) Turbo (15% of new cars) Efficiency is all about what engineers call “specific power,” the output of an engine relative to its size. What they strive for incessantly is more output out of smaller engines. Turbo units do just that. Instead of relying on pistons to “pull” air into a cylinder, the engines with turbo essentially have a really complex little fan that pushes—or compresses—air so that more can be forced into each cylinder, creating more power on the rare occasions that drivers ask for a little more pep. The share of new cars with turbo units has almost doubled in the past year.
U.S. automakers, meanwhile, are still playing catch-up on the efficiency front. Trucks aside, Toyota (7203:JT), Honda (7267:JT), and Mazda (7261:JT) were the mileage winners on the EPA list, each with an average MPG over 29. Ford finished at 27.4 miles per gallon, followed by GM (GM) at 25.6 and Chrysler at 24.7.
