I highly recommend dry graphite. You can find this in most automotive and industrial supply retailers.
Unlike other lubricants that attract dirt and grit because it stays 'wet' and oily, graphite only lubricates. The carrier evaporates quickly leaving only slippery dust that coats all surfaces.
I lubricate all of my locks and tumblers every Spring and Fall.
In the ignition be careful. While you can wash it off it is very difficult and it stains grey. So use lots of small squirts and even place an old rag on the floor in case it drips on the carpet.
On the outside locks place the rag below the lock to catch anything that may get on the paint and spay liberally inside the tumblers. Hold the cloth there for a few minutes. Then wipe the surface of the lock clean.

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I don't know the same things that you don't know.

Shayne

85 W126 SD OM617.951
87 409D 650S OM617.913
93 E34 Touring M50B25TU
02 E46 Sport M54B30TU