It's changing - manufacturers are definitely cracking down. This particular person did all of his own oil changes and kept good records with receipts of part purchases. Claim was ultimately denied due to insufficient evidence, but the dealer was able to workout a goodwill arrangement that covered most of the repair.
You bring up a good point about DIY oil changes. They will try to hold it over your head, regardless of the type, weight, or brand that you claim you used.
In that scenario, you have them take a sample or do it yourself, to cover yourself. They can't do much at that point. Once they see the oil is legit (approved and related to your oil receipts), they can't make much of a case. If the oil is not approved, that's a different story.
This person had UOA's. There was no way to ultimately prove that the work was done, or that the oil samples were from the vehicle in question. Absent of a professional shop's service receipts, there was doubt. Luckily the repair was mostly goodwilled.
