I just purchased a 2014 Cruze sedan for my daughter. The car was a lease return and had less than 9,000 miles on it. It was in great condition and had all the bells and whistles. I took it in for an oil change and the attendant at Jiffy Lube told me Chevy recommends synthetic oil. Is this necessary? Also, that he had trouble with the drain plug and that I should order a new one before the next oil change. Is there an after market source for the drain plug? Thanks.