ac compressor oil fill

[memyself4]

Installing a recon AC compressor in my B5.5 1.9tdi (2002). Any idea how I fill it with compressor oil ? Do I just pour in 3oz into the low side port?

Also it says I should use Denso ND8 oil which is about £50, but seems to be just the same a synthetic PAG145 oil ? that costs £8 !

Thank