A word of warning re OEM vs AGM 12v battery

Lots of people on here recommend just replacing your crappy OEM 12v battery for an AGM. We were having battery problems with our car and we swapped it but continued having problems. I made an appointment with the dealer to get it checked out, and they said that because my battery was still under warranty but I’d swapped it out, they’d no longer cover the diagnostic appointment, and if it turned out that there were any issues at all with anything related to the battery, we would be on the hook for paying for those repairs. Luckily, I was able to go back to the store where I’d dropped off my old battery and get it back. I reinstalled it in the car and didn’t have to pay for the diagnostic. (They also didn’t fix anything - they just charged up the old battery and said if it happens again then they might be able to replace it under warranty.)

Anyway, I just wanted to let people here know that if your battery is still under warranty, you should keep it until your warranty runs out, even if you don’t have it installed in your car.