I agree that WD40 is great for freeing up sticky door locks, but a word =
of warning. The combination of the old gunge in the lock and the WD40 =
makes a great grinding paste which will in time completely wear out your =
door-lock.
So, after you have got the lock free, it is essential that you use a =
good lubricant. I would recommend ATF oil (automatic transmission oil) =
as this has very good lubricating qualities and at the same time it does =
not freeze. It is much better than the commercial de-icers which are =
usually of the same type as WD40.
As I live in Sweden, frozen locks are a common problem in the winter, =
but since I started using ATF oil in the locks, I have had no problems =
even down to minus 30 Celsius (that's minus 22 F, for those of you who =
keep hanging on to antiquated measuring systems).
To get the oil into the lock, I have yet to find a better instrument =
than a medical hyperdermic syringe. The needle reaches into the deepest =
recesses of the lock.

Harley Thomas, Uppsala, Sweden
87 Caravelle
88 Caravelle
62 Beetle