A couple drops of oil is plenty to lubricate any gun. And I mean drops spread out in the various parts that need lubrication.
Excess oil attracts dirt, lint, powder fouling............... it gets on your clothes. It gets sprayed around when you fire it..............
That being said, it is important. Even critical.
But in moderation.
Light means light.
You know the rest. In the books you have read
How the British Regulars fired and fled,
How the farmers gave them ball for ball,
From behind each fence and farmyard wall,
Chasing the redcoats down the lane,
Then crossing the fields to emerge again
Under the trees at the turn of the road,
And only pausing to fire and load.