RECOMMENDATION:
Flush system and replace filters when converting unit to a different oil

REAL WORLD SCENARIOS:

Oils With The Same Base:
1. Drain
2. Fill
3. Replace oil filter

Petroleum To Synthetic:
1. Flush unit
2. Replace oil filter
3. Replace separator

PAO To Diester:
1. Drain
2. Fill
3. Replace oil filter

Diester To PAO:
1. Drain
2. Fill
3. Replace oil filter

Diester To Polyglycol Or Polyglycol To Diester:
1. Drain
2. Fill
3. Replace oil filter

PAO To Polyglycol Or Polyglycol To PAO:
1. Flush system with diester!!!
2. Replace oil filter!!!
3. Replace separator!!!