I agree with everything you say but its theorical .... yes car manufacturer will have to prove that but to whom ?
A judge ? because you know like me that they can drag you forever and raise sky high your level of stress and so, even if you have the law on your side
real life experience might be whole of a lot different , thats what I am looking for
I'll give you real life real world experience from one who does global warranty issues and expert witness testimonies in failures.
This is a scenario based on your post and more of a process map- not "legal" advice since there is no specific "thing.
You have a car with a failed engine under warranty. You run filter "X" and use oil "Y".
The "assumption" here is that the OEM says the filter failed causing the damage, not a failure of the engine proper and will not honor a warranty. ( getting out of it) ( we will assume the company simply refuses to discuss it further)
(This is where people like me usually get involved)
You have every right to challenge that but the burden of proof is on you to show either the company is wrong or at least has a degree of responsibility. The company walks into the game as an 'expert" under law so you will need an 'expert' to challenge them.
In order for you to do that you will need to forensically examine all components to the failure ( the engine, the car history, the filter and the oil).
OK, you did and your 'expert' says its the filter ( lets say internally collapsed)
Now the OEM says go sue the filter manufacturer and they are off the hook.
repeat all above steps
The filter OEM says the oil chemistry degraded the filter so go sue them.
repeat all steps above
Warranties are tricky things but they generally only prorate replace an article against defects in material/workmanship with no further liability. State/Federal laws ( vary by state) also determine limits too so what may work in Ga. might not even be possible in Wa. (Warranty is its own science)
Bottom line is, in every adverse scenario, YOU will be the claimant/plaintiff and the burden of proof is on you ( and expense)
I can tell you that "proving" ( to a legal standard) that part "X" caused something (to the legal standard of preponderance of evidence or beyond reasonable doubt if criminal) is a VERY high bar indeed.
So, if a company really stands their ground- you would need to make a true value based "is it worth it" decision to proceed.