The gap in customer satisfaction between the Detroit Three and Asian automakers is widening, according to a new survey by the American Customer Satisfaction Index.

The scores of five out of eight domestic brands declined in ACSI’s latest quarterly survey, conducted from April 6 to May 22.

The decline in customer satisfaction is not a serious threat yet for General Motors, Ford and Chrysler, but could quickly become a problem if it continues to drop, said Claes Fornell, chairman and founder of ACSI.

“I don’t think Detroit can afford to slip back further,” Fornell said. “We know that repeat business is important to every automaker, and that decreasing customer satisfaction makes it that much harder to get customer back.”

A closer look at the data show that some domestic brands actually improved from a year ago. GMC rose from 80 to 85, tied with Cadillac — just behind Subaru, Toyota and Honda at 86. Ford matched the industry average of 83, as did Chrysler brand, which jumped from 78 to 83.

The three brands that declined most were Chevrolet (79 from 84 a year ago), Jeep (80 from 83) and Dodge (79 from 81).

As recently as 2010, Asian and domestic automakers were tied in customer satisfaction, but Asian automakers have now re-established a significant advantage. It is worth noting that the survey omitted Lincoln, which might have boosted Ford’s corporate performance, and left out Scion, Toyota’s entry-level brand that generally has not established the type of reputation of either Toyota or Lexus.

Fornell said he suspects that the score declines are caused by a rising demand for cars and trucks that has caused the Detroit Three to rapidly increase production, hire new workers and to ask suppliers to do the same.

“I think it is probably due to the fact that they are running plants at a little bit more than full capacity, making it harder to get everything right,” he said.

Mercedes-Benz scored the highest on the survey with 88, followed by Lexus at 87.

ACSI’s August report on automobiles was based on phone interviews with 4,078 randomly selected customers.

Overall, the automotive industry is doing pretty well. Over the last five years, the average ACSI score has increased from 80 to 83. Customer satisfaction of the automotive industry ranks fourth of 43 industries that ACSI tracks.

The airline industry, with an overall score of 69, ranks fourth from last, just above social media, subscription TV services and Internet service providers.