Among the many substances emitted by autos back in the "good old days" were the refrigerant gases that would leak from older auto air conditioners. Freon, also known as R-12, was replaced starting in the early 1990s with R-134a, which did less damage to the ozone layer.
The new gas, HFO-1234yf, breaks down far faster in the atmosphere than today's R-134a, and will reduce the amount of airborne refrigerant from the new cars by more than 99 percent.
Supplied by Honeywell, the greenhouse-gas-friendly HFO-1234yf refrigerant breaks down in just 11 days, versus its predecessor's 13 years. This cuts its rating on the global warming potential (GWP) index from more than 1,400 to just 4.
Why make this change? In part, because the U.S. Environmental Protection Agency (EPA) awards carmakers credits for improving the environmental performance of refrigerants, helping the vehicles to meet limits on overall emissions of greenhouse gases like carbon dioxide.
GM says its vehicles will "significantly exceed" the target reduction of 40 percent in fuel usage by 2016.