Wondering if anyone else had this question/ experience... I read many conflicting articles on line and finally pulled out the manual that says "requires a 2032." Funny, to check, I got smart and opened both of my 2 key fobs,.. with further confusion. One actually has a thicker 2032, and the other key fob has a 2025. The 2025 seems loose, but the FOB works fine. I think the 2025 was put in the 1 key fob I had with me during the last service. Anyway, surprised it does not matter? Oh, an surprised they charged over 10 bucks for the wrong battery.... Also, Costco sells a 10 pack of 2032 Duracell's for 8.99 on sale,... OK, just sharing!

I was literally about to research this, time to change all my car key batteries. Sounds like the 2032 is the move

2032 on new style W213

2025 on older style W212

They are both 3V batteries.
W213 key fob takes 2032 which is thicker and because of that has higher capacity (235 vs 170 mAh). Should last longer than 2025.

Thanks everyone, yes, I am on track with the need for the 2032 - And wanted others to be aware.. Just thought it was strange that either seems to work, and Mercedes service people don't know the difference. At my next service I will kindly ask for a complimentary correct battery

but, as aforementioned, w212 has the 2025 -- because it's thinner and it fits
2032 will not allow the fob cover to close.

Mainly it's just a dimensional difference in thickness. Both are 20 mm in diameter, the 20 in CR20XX, but the CR2032 is 3.2 mm thick whereas the CR2025 is 2.5 mm thick.

Both are 3 V lithium cells but the CR2032 does have a slightly higher amp hour capacity due to the increased thickness.

I'm 99.9% sure I replaced my fob batteries with CR2032 cells. Didn't consult the manual, just replaced with like kind.

The W213 keys do take a CR2032 from factory I think? It is the previous model MBs with the older style key that takes CR2025. ...I think. CR2032 I remember were watch batteries or the Tamagotchi my kids used to play.