This came up in a thread in another forum I visit:"""wouldn't get too worried about the cat convertor issue. The oil additive that poses a risk to convertors is zinc dithiophosphate (ZDP). This is good stuff, an anti-wear additive. If you overfill your crankcase or change oil too frequently cat convertor damage can result. This is why most auto manufacturers are recommending higher quality oil and longer oil change interval.""" Never heard too frequent changes cause damage, other than financial, what do you think?