[ovp0]

I just took my 2005 Blazer in for it's first oil change and to repair the issues with the fuel guage and tank today and the dealer told me that I should change the rear differential flud at 5,000 km. I didn't see this in the owners manual so I declined since there is only 4,000 km on it now. The cost was about $140.00 but that depends if it is synthetic or not. How do I find out the type of fluid ? and is this a real requirement? Any comments..........