What are the advantages of polyalkylenglycol oils compared to thickened white oils in hypercompressors?

PAG oils have better pumpability performances and are thus most appropriate in particular for tubular LDPE/EVA manufacturing where the compressor can reach up to 3000 bar. 
PAG oils ensure better anti-wear performances thus resulting in a very good lubricity: this is very important in order to guarantee extended packing lifetime and to ensure the right film thickness on the plunger. PAG oils are insoluble in hydrocarbons which makes them more resistant to the gas (ethylene but also vinyl acetate monomer) washout, resulting in a lower overall consumption. 
In particular for EVA manufacturing, PAG oils have been designed to have very good anti-corrosion properties which protect the mechanical parts from the polymerisation's acidic by-products.