I suppose the info should be in the book of words -
I changed the oil on a peugeot 306 HDI the other day - I put the 'seam' under the bolt head and tightened carefully (you can feel the washer crushing) and then gave it a technical tweak
But for aviation applications there should be a torque loading for a crush washer - and they are usually a fairly low torque loading.
As a rule I do not try to remember torque loadings but ISTR that Canberra brake banjo crushwashers were 15 Lb Inches.