Carmakers already concerned about tough new 35mpg fuel economy standards set to roll in by 2020 now have something else to worry about with the announcement today by an EPA official that passenger cars and light trucks may have to average 75mpg by 2030. The latest statement follows a previous announcement from the scientific community that world oil usage could rise to 120 million barrels a day by the same 2030 cutoff date - up from 85 million barrels at current levels.

Speaking at the SAE International World Congress today, the U.S.’ director of the Office of Transportation and Air Quality, Margo Oge, said a 75mpg target is necessary to meet a widely backed scientific-community proposal to cut greenhouse gas emissions by 50 to 80% by 2050.

"There are a lot of strategies you need to consider - both engines and fuels," she explained during an interview with The Detroit News. "Carmakers need to be thinking of those investments for the long term basis," beyond the current 35mpg CAFE energy bill.

America’s transportation sector accounts for two thirds of U.S. oil use and a third of its greenhouse gas emissions, so any improvements in fuel economy standards will have a major effect on the country’s dependence on oil and pollution levels.

As for the current 35mpg standard, the National Highway Traffic Safety Administration is expected to release its proposal for 2010-2015 interim fuel economy increases as soon as next week.