I read an article about a covered investigation at Jiffy Lube, where they sometimes charge customer for oil change and other jobs but did not do anything.

http://www.knbc.com/news/9265933/detail.html
http://www.knbc.com/mechanicinvestigation/9879404/detail.html

The investigator marked their parts, which were supposed to be replaced. After picking up the car, they checked and found the old parts still with intact marking, although the parts and labor were billed. Those frauds were discovered not once by the investigators, but repeatedly.

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1996 E320 since 1/16/08, 171K miles as of Feb 2011

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1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE