This is a really common dilemma in industrial settings! I've been in similar situations where a third-party part seems like a no-brainer - better performance at a lower cost. But that warranty threat makes you pause.
First, let me share something important I learned: Under the Magnuson-Moss Warranty Act (in the US), manufacturers generally can't void your entire warranty just for using third-party parts. They can only deny warranty claims if they can prove the aftermarket part actually caused the damage. So that 'voids the warranty' language might be more of a scare tactic than legal reality.
Here's how I'd approach this ethically and practically:
1. Check the actual warranty terms - sometimes the language is more nuanced than 'voids everything'
2. Document everything - keep records of the OEM part's performance issues and the third-party part's specifications
3. Consider the risk - if the machine is critical to your operations, is the performance gain worth potential warranty hassles?
4. Talk to the OEM - sometimes they'll work with you if you're transparent about performance issues
Ethically, I think transparency is key. If you're maintaining equipment for someone else, they deserve to know the trade-offs. Personally, I've found that when third-party parts are truly better and properly documented, most reasonable manufacturers won't fight you on warranty claims unless there's actual damage caused by the part.