Costlier imports have helped models such as the Chevy Cruze gain on Asian competitors.

A weaker American dollar is helping the Detroit Big Three automakers get back on their feet.

With the Korean Won and the Japanese Yen gaining on the dollar, imports by Asian automakers have become more expensive and that is getting reflected in their showroom prices.

Now, the gap between the price of import models and domestic ones is at the highest its been in 12 years. The average import sells for $31,536 in the United States compared to $23,922 for a domestic vehicle. That large gap is helping models such as the Chevrolet Cruze gain on its Asian competitors in a tough American economy.

But that gap also represent a change in the supply end of the business. As the tsunami disaster that hit Japan earlier this year curtailed exports and hit supplies for dealers of Japanese brands in the United States, that also helped domestic automakers who had ample supply of less-expensive cars. The share of imports that were premium models from Europe also grew as a percentage of all imports, serving to raise the average import price.

The weak dollar has helped brands like Chevrolet, which sold a record 1.2 million units in the third quarter of 2011 - a large chunk of those to customers in their home market. GM as a whole has gained one point in market share at home this year, through the month of September, which now stands at 20 percent. Ford's share of the market has also grown slightly to 16.7 percent.

Gallery: Weak U.S. dollar helps Detroit automakers gain share