My wife's 2005 clk500 has only 5200 miles on it but she has had it for 2 years. I brought it in to the dealer and wanted an oil change. Dealer said I didn't need it. If I go to a private shop can the computer be reset? Does this have an adverse effect on anything else such as the warranty. Is it mandatory to have oil changes done by Mercedes. Thanks

 

5200 miles isn't enough to warrant an oil change on ASSYST usage grounds.
However ASSYST also takes account of time on low mileage vehicles and my experience is that a service (= oil change+) is called for at 2 years.
ASSYST will tell you how many days are left before your next service if you access it using the instructions in the handbook.
At about 1 month from when service is required the ASSYST system will automatically tell you with a "Beep" and a spanner message when you start the car.
In the UK warranty used to be linked to having the car correctly serviced by MB. The law has now changed and so long as the car is professionally serviced this SHOULD NOT adversely impact warranty. Not sure what the situation is in the USA. Take care!

It is EXTREMELY important to carry out oil changes at the required points (or more frequently if you prefer). It is also EXTREMELY important that you use MB recommended oil manufacturer, type, grade and also use the appropriate OE filter.

For the sake of a few pounds I would generate goodwill with the dealer (if in reasonable proximity) and get them to do the job. Then if the worse happens you will be covered without question.
Stuart