If you rub the key with a graphite pencil and insert into the tumbler -repeat 10 times, you can't over do it and get too much in there and is all that's needed. If you get a tube of graphite and squirt it in the tumbler, you are probably putting in way too much, besides bing wasteful, it won't lube any better and could actually make it worse, as some have found.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Hmmm. So now I'm worried about all the graphite dust in my ignition. Should I just blast with some air?

I wanna get it out

Best not to disturb what ever debris that's in there like blowing compressed air, which may cause it to jam depending where the debris lands. If the lock is working well, just leave it alone.

The best thing you can do is replace the tumbler with a new one then never use any liquid lube, only a tiny bit of graphite from a pencil every few months.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

WD-40 is what I have been using since the 1970s on all of my Locks especially those exposed to the outdoors. When I mentioned that on this forum I always got the parroted response to use graphit. Nice to know that there is a knowledgeable old-school locksmith that is not stuck on the Graphite solution.
My gripe with graphite it has zero rust protedtion.

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84 300D, 82 Volvo 244Gl Diesel

Locks are made of rust free materials and should not need any rust protection.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Cheap pad locks have Steel in side. Usually the cross bolt is steel as well as the hook shaped part (don't know the name for that).

Automotive locks use steel wafers instead of pins.

Even brass lock pins and other parts can corrode.

The springs inside of locks are usually steel.

As an added bonus the liquid WD-40 can flush out stuff.

Note that WD-40 does not give really good protection. Only about 3 months in a climate where it does not rain much.

Graphite works OK on most household door locks because the lock Body and tumbler are often some sort of pot metal and there is little steel inside of them.
The Pot metal can corrode a little but the clearances are generous and the locks are usually sheltered some from the elements.

Also household door locks are usually used frequently keeping what little corrosion that can happen to a minimum.

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84 300D, 82 Volvo 244Gl Diesel