Well, replacing your O2 sensor is the most costly endeavor, relatively speaking. I think they start at around $60 at Advanced Auto Parts. However, if the O2 sensor was faulty it would throw a Check Engine Light. Where as a fuel filter or spark plugs won't necessarily do that. Your car has 98k miles. The O2 sensor should be replaced every 100,000 miles. This is covered by Inspection II at your BMW shop...so, if you do most of the work yourself then go ahead and replace it. |