Had oil change 7 times in one year and each time they indicate at the place I get oil changed that it is a quart or more low before 3,000 miles of usage after oil change. My car is suppose to take unleaded gas or higher and it knocks if I use unloaded. Now my catalytic converter is going out and it is not covered under warranty unless it is consequential to other problems. Well there appears to be engine problems that are not being addressed and I have a warranty and have taken it in. But they do not look any deeper into the problem except for computer scan and the warranty people won’t give me any answers on what they will do if there is engine problems.