I hate to admit this, but GC gold is costing me money. My MPG has dropped 2, or maybe even close to 3 MPG. I'm almost done with my tank, so I don't know exactly yet. I do know however that I am almost 50 miles under what I am usually at. I don't consider external conditions like driving habit, weather, gas type, etc. to be a factor since those have been constant. The oil is the only differing factor. On the good side though, GC gold has done wonders for my car. Very quick starts, quieter engine, and good protection. The dilemma now is whether GC is worth the extra $11.xx a month in wasted fuel.