I purchased my 2011 new last January. I do a lot of highway driving and I am concerned about how often I have to change the oil. I now have 30,000 miles on it and I have had to change the oil every 5000 miles using the Oil Life Monitor system on the DIC . I would think that since the Terrain requires synthetic oil one would get more miles between oil changes. I always got 7500-10000 miles using the OLM on my prior Buick Rainer which used regular oil. This an added expense I was not planning on. I would like your feedback on whether I am off base or if something needs adjusted.