Hi Andy
I presume you are talking about the condenser O-rings and not the compressor O-rings ?
IF the condenser O-rings then use a little red rubber grease on them.
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If it's the compressor O-rings then just use the oil that's in the compressor dip your finger into the hole and smear the oil around the O-ring
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Changed mine out a few days ago due to a leak, i am about to strip it down sometime today.