Vehicle emissions are down and fuel economy is up, EPA reports

The Environmental Protection Agency released its emissions and fuel-economy report for 2010. Adjusted emissions are down across the board, at 395 grams of carbon dioxide per mile. That's a record low for the post-1975 database.

The report included several highlights. Besides the fact that emissions are down and fuel economy is up, the truck-segment market share is up; so are weight and power across all segments. Additionally, the new technologies are quickly gaining market share.

According to the report, since 1975, CO2 output has gone through four phases. From 1975 to 1981, it decreased rapidly; after that, it decreased slowly until it reached a valley in 1987. It increased again until 2004, then started going down through 2009. And as CO2 emissions have decreased, adjusted fuel economy has gone up, now to an average of 28.4 mpg for cars.

The light-truck segment—in which the EPA includes truck-based SUVs, minivans and pickups—has grown 5 percent from the 2009 model year, but the numbers are skewed for that year because of the economic turmoil. Truck sales in 2010 didn't reach 2008's all-time high levels. For the 2011 model year, truck market share is expected to hit 38 percent, based on production projections by automakers.

In an interesting fact revealed by the report, even though fuel economy is up and CO2 emissions are down, power and weight have been increasing almost continually for the past 30 years. That means the new technologies such as multivalve engines, direct injection and cylinder deactivation are not only working but are being widely adopted.

In terms of market share, the number of direct-injection engines doubled for the 2010 model year and are on pace to triple for 2011. Turbocharging is expected to double, as are engines with cylinder deactivation. Multivalve engines, which made up 62 percent of the market in 2004, now make up 85 percent. Just 3 percent of cars had a six-speed transmission in 2004; that number has grown to 52.4 percent now.

So what have we learned? Our gasoline engines have made giant steps in the past 10 years. And with hybrids only occupying about 4 percent of the market, that's what we'll be working with for the foreseeable future. If the trends continue, noting that the power of gasoline can only be pushed so far, we wouldn't be surprised to see 50-, 60- and 70-mpg vehicles in the near future with some other sort of new technology to squeeze a few more calories out of every gallon of our favorite petroleum-based fuel.

By Jake Lingeman