This question simply can't be answered by anyone here. Whether a dealer can get a warranty claim approved by the manufacturer is not a simple thing - the dealer really is the warranty gatekeeper here even though they aren't the ones that approve it in the end. As much as everyone that chimes in thinks that they have to prove this or that, that could require a lawyer and a courtroom something most aren't going to bother with if it's denied. One thing that gauarntees (at least to the extent you can) a smoother warranty claim process in the event of a major powertrain failure that the lubrication *could* come into question is using the oil that the manufacturer calls out in the owner's manual and having good records of the maintenance DIY, third-party shop, or dealer. If you are comfortable that this won't be an issue, then of course, do what you want. Personally? I can't imagine a situation where you would 1) have a big engine issue AND 2) have to provide records AND 3) have the dealer/OE tell you that using 5W30 vs. 5W20 denies it (if they even noticed this level of detail beyond "I changed my oil"). But again, that's me, not you...it is possible and that's the crux here.