Top-selling fuel-efficient vehicles, 2010

The biggest passenger vehicle markets have progressively seen an increased penetration of highly fuel-efficient and technologically advanced automobiles (defined as vehicles having the lowest emissions of CO₂ in g/km). But experiences differ significantly across them. An ICCT analysis of vehicles sold in the European Union, the United States, India, China and Japan during 2010 shows intriguing trends in how OEMs are attempting to both meet emission standards and appeal to customers.

The only vehicle that is offered to GHG-conscious buyers in all five markets is the Toyota Prius, which, depending on the exact model specification, emits between 89 and 110 g/km of carbon dioxide. The Prius is a midsize gasoline hybrid electric vehicle, employing continuously variable transmission (CVT) and idling control features (commonly known as start/stop systems), which improve the performance of the vehicle and decrease the amount of emissions. In fact, the CVT and idle control functions are popular across many other low-emission vehicles.

Aside from the Toyota Prius, top performers from a carbon dioxide perspective in the European Union (EU) are diesel-powered, manual-transmission vehicles, which use various additional technologies like engine downsizing and regenerative braking to assure optimal fuel usage and low emissions. (Plug-in electric vehicles, battery electric vehicles, and fuel cell electric vehicles were excluded from this analysis, due to their generally very low sales numbers in 2010.) In many of the latest-generation cars, lightweight materials and special low-friction tires further augment the driving efficiency. The EU is the market that sees the largest OEM variety of vehicles emitting less than 100 g/km, with models falling mostly in the small segment. The lowest emitting vehicle is the two-seat Smart Fortwo, with an engine displacement of only 0.8 liters.

All of the least-carbon-emitting passenger vehicles in the U.S. are midsize gasoline hybrid electric models, utilizing CVT technology. In the U.S. even the least CO2 emitting passenger cars maintain emission levels above 110 g/km. In parts this is due to differences in the test procedures and test cycles. All of the low-emission models sold in the U.S. utilize regenerative braking and variable valve timing.

An intriguing development in the fast-growing markets of India and China is the emergence of low-emission models of OEMs, typically focused on the domestic scene, like Tata and Jianghuai. Tata Nano and Jianghuai Yueyue/Tojoy measure up very well to imported low-carbon cars (98 g/km for the Nano and 118 g/km for the Jianghuai models). Most of the low-emission cars in these regions are small-size cars with an engine displacement below 1.5 liters, or even below 1.0 liters. In addition, the small and mini segments in India, China, and Japan contain the largest concentration of low-emission vehicles. Continuously variable transmission is only beginning to emerge as a technology of choice in India and China, while a large share of the low-polluting vehicles available for purchase in Japan already have that option.

Low-CO₂ passenger car models worldwide