The German luxury automaker scored 88 on a scale of 0 to 100, ascending to the top spot after Lincoln, last year's winner, stopped being measured because of low market share.
Lexus remained the runner-up, scoring 87, down 2 percent from 2012.
Third-place Subaru, Toyota and Honda — the highest ranking non-luxury nameplates — each scored 86 — 3 points above the industry average.
Overall, European manufacturers ranked first with a satisfaction score of 84.7, followed closely by Asian automakers with a score of 84.1, and a score of 82 for U.S. companies.
The American Customer Satisfaction Index, based on phone and e-mail interviews with 4,078 recent customers randomly picked between April 6 and May 22, found that customer satisfaction with automobiles and light vehicles dropped 1.2 percent to an industry wide average of 83, down from 84 in 2012.
The index was started in 1994 and measures customer satisfaction with the quality of 20 foreign and domestic nameplates, along with other factors such as price and the dealership experience.
GMC, 85, tied with Cadillac in fourth place and was the only non-luxury domestic brand north of the industry average.
Ford and Chrysler, which gained 5 points from 2012, tallied scores of 83, matching the industry average.
Dodge and Chevrolet came in last with scores of 79, just below Jeep, with a score of 80.
GMC and Chrysler had the largest percentage increases, both 6 percent. Buick — which scored 82 — and Chevrolet had the largest declines, at 6 percent.
ACSI Director David VanAmburg said it's unclear how Ford's decision to reduce the stated fuel economy of the C-Max hybrid could impact next year's rating, saying only it wouldn't be "terribly helpful."
He said the index doesn't focus on a particular model.