Ever since the first Honda Insight and Toyota Prius arrived on U.S. shores, hybrid vehicles have been among the most efficient vehicles on the road.
The latest Toyota Prius is rated at 50 mpg combined by the EPA, a figure that only plug-in vehicles currently top.
But in other countries, the Prius has even higher official economy figures. And in some, the real-world savings are even greater than they are in the U.S. too.
Hybrids are typically at their best in city driving, particularly full hybrid vehicles that offer a mile or two of all-electric range.
In countries like India and China, where awful city traffic conditions mean hours of idling on every commute, a hybrid's ability to run on all-electric power really comes into its own.
Researchers at the Lawrence Berkeley National Laboratory have found that these driving conditions mean the average hybrid is much more efficient in these countries than it is in the U.S.--where generally, all but the worst traffic snarl-ups move at a reasonable pace.
So stark are the hybrid's benefits in Indian and Chinese traffic conditions that it may bring about changes in the test cycles used in each country.
Currently, Indian test cycles show around a 29 percent fuel saving for hybrids, compared to conventional vehicles.
It's tricky to test real-world savings against conventional vehicles, as every car is different. It's no use running a Prius in the tests, for example, as the Prius is several classes bigger and many times more expensive than India's best-selling vehicle, the Maruti Suzuki Alto.
To get around this problem the two researchers, Anand Gopal and Samveg Saxena, tested improvements using a powertrain simulation model to create a hypothetical hybridized version of the Indian and Chinese best-sellers--the latter the Buick Excelle.
Maruti Suzuki Alto 800
That allowed them to isolate the improvement from hybridization, separated from other factors. Using such tests, hybrids returned a 47-48 percent improvement in Indian traffic conditions.
In Chinese conditions, the improvement was even greater--saving 53-55 percent in fuel.
By comparison, hybrid vehicles in the U.S. are rated around 40 percent more efficient than conventional counterparts.
Three main factors came to the fore: A hybrid's ability to reduce demand on the engine when moving, its ability to turn off the engine entirely in some situations, and the extra energy regained through regenerative braking.
The results are impressive enough that the Indian government is now analyzing the data, helping it refine a national plan to put 6 to 7 million hybrid and electric vehicles on the road by 2020.
Official fuel consumption figures are often wide of the mark. In Europe, for example, vehicles regularly fall short of official economy figures, sometimes by as much as a third.
Japan's oft-quoted JC08 test cycle is heavily city-biased, and probably closer to India and China's traffic conditions than most--the Prius, rated at 50 mpg by the EPA, officially hits 77 mpg in JC08.
In the U.S, official EPA ratings tend to be fairly accurate--and issues only arise when vehicles miss out on their official numbers by quite some margin, highlighted in recent Ford and Hyundai/Kia cases.
With personal transportation set to increase in both India and China though, hybrids could be a vital tool in ensuring emissions and fuel use doesn't skyrocket over the next few decades.