I'd like to get everyone's opinion on this. I last changed the oil in my 2.2L Ecotec Malibu 1/28/12 with Pennzoil Ultra 5w30 at 24,446 miles. It is now at 29,555 miles and the OLM is at 24%. The car sat mostly unused (about 150 miles put on it total) from April to December 2013. The filter has not been changed. Is it safe to assume this oil has still been good on the engine all this time? I plan on changing it very soon...