Detroit — Here we go again.

When first enacted in 1975, federal mpg standards discriminated against American manufacturers who offered a broader range of models. The so-called CAFE standards forced U.S. manufacturers into costly adjustments even as their upstart Japanese counterparts did not, giving foreign competitors and their smaller vehicles a leg up in the U.S. market.

Thirty years later, the feds’ new CAFE laws will once again put American automakers at a disadvantage — even as Washington has spent billions bailing out the industry. The evidence is in EPA’s fuel-efficiency numbers released last week, showing the Detroit makers at the bottom in overall fleet efficiency — with Honda, Hyundai, and Toyota leading the pack.

This means it will be that much more costly for GM, for example, to meet the new fleet standard of 35.5 mpg by 2015 from its current average of 19.9 mpg. Honda, by contrast, will have an easier road geting there from its current average of 23.6 mpg.

If Washington were truly interested in helping America automakers, they would lessen (or eliminate altogether) mpg standards, playing to the domestic manufacturers strengths in a market in which consumers have traditionally preferred larger vehicles.

These days, however, green piety takes precedence over common sense.