I agree with this statement for the most part. If a company requires the use of an OE part only, they must provide said part free of charge. However, warranty can be denied for use of unapproved aftermarket items. Example - GM requires the use of the correct weight of Dexos approved oil. If you choose to use a non Dexos certified oil - your warranty can be (and has been voided). There are aftermarket oil filters that have proven to have caused catastrophic engine failures (I've seen the GM bulletins). I'm not sure how GM handles warranty claims on these - but I used to let my repair shops know about aftermarket filters that did cause this kind of damage so their customers would not suffer this kind of failure. Example, the most recent situation I can remember, the "B" line oil filter manufactured by WIX for use in certain Hyandai/Kia vehicles was documented to collapse and cause catastrophic engine failure. When this problem was identified, I notified all my customers of the problem and strongly urged them to not use this filter and recommended using the OE oil filter (in addition to ACD, MTC and Mopar OE parts, we were also an authorized distributor for Hyundai/Kia OE parts). I don't know how the OE manufacturer handled warranty claims on failures that were documented to have been caused by an aftermarket part. It could be that they covered the claim and went after WIX for reimbursement. I also remember an ACDelco bulletin for failures by certain brands of aftermarket filters for the PF 2257G filter used on the 1.4L Turbo. As I owned one at the time, I always brought an OE filter when I had my oil change done by one of my customers - just to make sure I didn't have the problem.