I recommend three things.

1) Get a can of the official MB cylinder lock lubricant, cost is ~$10, it has a key-shaped application tip on a pressurized little can so you get all the lubricant exactly where you want it. It lubricates and protects against freezing.

2) Use only a real MB steel key, which won't leave metal bits behind like a copy will. Save your copy as an emergency spare. Take your proof of ownership to the dealer and spend the ~$25 for a proper key.

3) Don't hang a heavy key ring from the ignition key chain (the extra weight causes extra wear).

IF your ignition lock ever exhibits the slightest bit of balkiness, and you have to work a little bit or use extra pressure to get it to turn, PLEASE immediately order a new ignition tumbler from the MB dealer, and install it when it arrives. It will be VIN matched so same key will work in the doors. Failure to heed this little warning sign from your ignition may cause $500 to $1000 when it could have cost $100.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC