Despite having to deal with a wider range of remediation issues than its major bank rivals, Commonwealth Bank continues to have the highest customer satisfaction rating among the Big Four and in recent months has been pulling away from the others.According to the latest Roy Morgan Research consumer banking customer satisfaction survey, CBA's rating increased by 80 basis points over the three months to September to 82 per cent.It was the only big bank to improve its rating over that period. ANZ's rating is 78.8 per cent, NAB's is 78 per cent and Westpac's 77.3 per cent.The big banks achieved a 20-year peak in their satisfaction scores last year. Since then NAB's score has fallen 3.4 percentage points, Westpac's 2.7 percentage points, ANZ's 70 basis points and CBA's 50 basis points.Home loan customers are a drag for the big banks, giving their banks ratings that are well below those of non-mortgage customers. CBA's home loan customers give it a rating of 77.7 per cent, while its non-mortgage customers give it a rating of 82.9 per cent.Among other banks in the survey, Victoria Teachers Mutual Bank's satisfaction rating was 95.3 per cent, Greater Bank's was 95.2 per cent and Bank Australia's was 93.7 per cent and Teachers Mutual Bank's 93.5 per cent.The Roy Morgan figures show that smaller financial institutions have a higher proportion of "advocates" among their satisfied customers. If a customer gives a bank a rating of nine or ten they are classified as "very satisfied" and are considered to be likely to recommend their bank to others.Bendigo and Adelaide Bank has a satisfaction rating of 89.2 per cent, made up of 38.7 per cent who are fairly satisfied and 50.5 per cent who are very satisfied. This is the highest proportion of very satisfied customers in the survey, followed by ING Direct with a very satisfied rating of 50 per cent.The average proportion of very satisfied customers among all banks in the survey is 35.9 per cent. For CBA the proportion is 34.9 per cent, for NAB it is 31.4 per cent, for ANZ 31.1 per cent and for Westpac 29.4 per cent.Roy Morgan industry communications director Norman Morris said: "Many banks are now looking at advocacy as a measure of their performance as well as satisfaction. There is great potential to increase advocacy by converting more of these fairly satisfied customers to very satisfied."