For adding oil, I would just do what the instructions say. Some compressors come pre-filled, some don't.

BTW I've still got original SS A/C compressors in both my 900s, but one has a long known very slow compressor seal leak for well over 10 years. At the moment the charge is down right on the hairy edge of allowing the low pressure switch to keep it kicked in for anywhere from 15-30 minutes depending on ambient temp. I'm debating at the moment on finally replacing the compressor or yet again just to having a purge and recharge done trying to get a few more years out of it. I'm at the 6 year mark after the last charge, so nothing to be proud of, but nothing fatal. Although I'm in a rather temperate weather zone and managed for decades without A/C in my 120, 140 and 240, it seems climate change keeps throwing us heat wave curve balls in recent years, plus once you have A/C it's hard to go back.

Now that I'm on a trip down memory lane, I'm sure many of us oldsters remember cars where flipping the front door window vents out backwards was all you had to give you a good breeze on a scorching day. The 2-doors also gave you the rear side windows to flick out. When the 140s went to the one piece door windows, they more than made up for it with dash face vents and also the manual front footwell side vents (closed off if you bought the A/C option). The 240s gave you the added option of a sun roof. With often less than 110hp, there wasn't a lot of extra power on the highway to drive a compressor.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now