My 83 has similar situation I think. There is a separate key to the door locks than the ignition because at some point a PO had to change the ignition out. So the later Ignition key does not work in the doors... however the older key does and does not work the ignition. Fortunately I have both though.

I ordered key blanks from Keymen.com and just had them cut at the local hardware store. But I had to have them cut both keys. One for ignition and one for doors.

In your case I don't know what to tell you if lubrication doesn't work. But prepare for the possibility that you have a similar situation. And the only thing I can think of to do is change out the exterior door tumblers to a matched set with key. Although its possible a locksmith might can make you a key... for the existing tumblers?

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1983 300D-Turbo - Deep Blue w Palomino MB Tex (total loss in fire 1/5/09 RIP)
1995 E320 W124 Polar White/Grey Mushroom MB Tex
2005 F150 Supercrew - Arizona Beige - Lear topper
1985 Piaggio Vespa T5 - Black and Chrome

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