Forget WD-40... Try white silicone grease.
It comes in a spray can, lubricates and protects in one spray. I've used it for years and it works great. Also used in door lock mechanisms (key holes) to prevent moisture buildup or icing over in harsh winter environments... works better than graphite or other solid lubes.

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William
76 240D - 550K miles
78 300D - 200K+ miles