In a 30-yr old MB, the "non-sterile" expired bandage that is wrapped up in a wrapper, tucked away inside a clean-dust-free first aid kit is probably the cleanest thing in the car. I wouldn't use a Kleenex out of a 30-yr old Kleenex box if I cut myself, but I'd certainly use the bandage.

With my W126, I opened the first aid kit and looked at what was inside. Went to Walmart, bought a $7 first-aid kit, and replaced any matching parts. Then I put anything from the Walmart kit into the MB kit that wasn't already there (ie. the Walmart kit came with tweezers, aspirin packets, etc.... so I said "why not" and threw them in)

I think that is the best thing to do with an old first aid kit. Keep the case and any literature, and just start replacing the band-aids, gauze, etc. I felt much better knowing the antibacterial cream was replaced with 4 "one-use" packs of Neo-to-go (Neosporin in travel size packs). There was a clear expiry date printed on the Neo so (had I kept the car longer) I would have just repeated the same swap in a few years with newer first aid stuff.

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'83 300SD 335,000km (207k) mi SOLD
'87 560SL 163,000km (101k mi) SOLD
'86 300SDL 356,000km (220k mi) SOLD
'92 500SEL 250,000km (155k mi) SOLD
'90 300SL 140,000km (87k mi) SOLD
'01 S430 260,000km (161k mi) SOLD
'03 SL500 167,000km (104k mi) SOLD
'07 S550 4MATIC 235,000km (146k mi) SOLD
'07 GL320 CDI 4MATIC 348,000km (215k mi)
'13 GL350 BlueTec 4MATIC 170,000km (105k mi)
'14 SL550 72,000km (43k mi)