Should I use copper slip

No IMHO. I've noticed an increasing tendency to smear car wheelnuts/studs with copperslip and have spent some tedious time washing it off with petrol without contaminating the brakes. I would use it on exhaust nuts and any stainless fittings you have used particularly where the stainless screws into alloy. Not needed on a cylinder head, clean and dry threads here. People claim that it prevents brake disc pad squeal. Utter tosh and even my local ford dealer puts a smear on my car caliper (without disassembling them) , probably just so I know he's had a look at them...................you can't fool me.

Previously david_evans wrote:

No IMHO. I've noticed an increasing tendency to smear car wheelnuts/studs with copperslip and have spent some tedious time washing it off with petrol without contaminating the brakes. I would use it on exhaust nuts and any stainless fittings you have used particularly where the stainless screws into alloy. Not needed on a cylinder head, clean and dry threads here. People claim that it prevents brake disc pad squeal. Utter tosh and even my local ford dealer puts a smear on my car caliper (without disassembling them) , probably just so I know he's had a look at them...................you can't fool me.

adding to the comments i was advised never to use it in the swinging arm pins/bushes [i was on witha velocette at the time] as it causes severe wear, probably not applicable tofetherbed bushes but worth knowing.

It is easy to over torque lubricated threads. If you look up torque tables, you will see different figures for dry and lubricated threads. And no, I wouldn't copper slip head studs.