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American automakers are losing the race to make more fuel-efficient vehicles
(www.theverge.com)
This is a most excellent place for technology news and articles.
On top of that average lifetime of a car in US is 12 years so those car's will be on the roads for a decade or two after exemptions are removed.
Much longer than 12, that's the average age (including new cars). This site says the average lifespan is closer to 17 years.