My Whirlpool dishwasher DU8500XB1 runs over 2 hrs reg wash!
Do I need a new timer, or some other part, or just some oil?

Here's the Whirlpool site's literature search page where you can get owners manuals for your machine:

Whirlpool Product Literature Search Results (http://shared.whirlpoolcorp.com/product_literature/search_results.jsp?searchTerm=DU8500XB1&siteCd=WHRCOM)

Here is the actual owner's manual:

http://shared.whirlpoolcorp.com/assets/pdfs/literature/Use%20and%20Care%20Guide%20-%203373739.pdf

The manual does have one suggestion for the cycle taking too long:

"Water temperature is too low -- If needed, turn home water heater up to ensure water entering dishwasher is 120°F (49°C) minimum. See recommended procedure on page 13. "

Be sure and check that out. I doubt that oil will do much. If your water is up to snuff, the timer cycle could be watched with a voltmeter.