By David Shepardson WASHINGTON (Reuters) - The chief executives of 18 major automakers and their U.S. units urged President Donald Trump to revisit a decision by the Obama administration to lock in vehicle fuel efficiency rules through 2025. In a letter sent late Friday and viewed by Reuters, the chief executives of General Motors Co , Ford Motor Co, Fiat Chrysler Automobiles NV, along with the top North American executives at Toyota Motor Corp , Volkswagen AG , Honda Motor Co , Hyundai Motor Co , Nissan Motor Co and others urged Trump to reverse the decision, warning thousands of jobs could be at risk.