2021 Nissan Rogue Warranty Concern

My wife has a 2021 Nissan Rogue with ~42,000 miles on it. For the past year or so, we’ve noticed the coolant level in the reservoir steadily dropping. I topped off once or twice but the level keeps going down (I know the coolant level fluctuates when the engine is hot vs cold and all measurements I’ve been taking have been during cold). There are no active leaks/drips of coolant anywhere and I’ve also pressure tested the system with no evidence of pressure loss. I am anticipating a small crack somewhere in the head/engine block.

We have until the end of July under powertrain warranty so brought it to the dealer to take a look at in late May. The coolant level was topped off before bringing it so they did their pressure test (which found no pressure loss) and looked for obvious leaks. They found no issues so they gave the car back to us and marked the level of the coolant in the reservoir for us to drive around and bring back if the level dropped. After about 1.5 months of driving it (relatively normal commutes with nothing longer than 45-60 minutes), I brought it back because the level was below the minimum fill line in the reservoir. Nissan is claiming that this is “normal” and they still can’t find anything wrong. I’ve argued with them multiple times since bringing it in initially but they have been increasingly difficult to work with. For context, I do all of my own work on my personal vehicles (2015 4Runner & 2001 Civic) so I have a very good understanding of a vehicles major systems.

What should be my next steps here? It’s pretty clear to me that they’ll need to take out the engine and potentially replace but getting them to commit to that seems far-fetched. They also said they would have to charge 8-10 hours labor to do that, and I have a feeling they’re going to look for every excuse to not have to change anything and we’ll be SOL for paying the labor they’ve done. I’ve documented everything with Nissan Consumer Affairs so far as well.

Currently trying to convince my wife to trade in the Rogue (especially considering Nissan claims there is no concern so we should get full value of the trade in).