Pick the oil currently in the sump and the oil you want to change to. Compatibility ratings apply to rotary screw, reciprocating, scroll, and vacuum pump lubricants of matching ISO grade.
Result
Top-up OK
OK to top up only
Miscible enough for emergency top-up (<10% by volume). For a full change, drain and refill with the new oil.
Full compatibility matrix
| from ↓ / to → | Mineral | Semi-synthetic | PAO | Diester | POE | PAG | Silicone | Food-grade | Phosphate |
|---|---|---|---|---|---|---|---|---|---|
| Mineral | OK | OK | Top-up OK | NO | NO | NO | NO | NO | NO |
| Semi-synthetic | OK | OK | NO | NO | NO | NO | NO | NO | NO |
| PAO | Top-up OK | NO | OK | NO | NO | NO | NO | NO | NO |
| Diester | NO | NO | NO | OK | OK | NO | NO | Flush | Caution |
| POE | NO | NO | NO | OK | OK | NO | NO | Flush | Caution |
| PAG | NO | NO | NO | NO | NO | OK | NO | NO | NO |
| Silicone | NO | NO | NO | NO | NO | NO | OK | NO | NO |
| Food-grade | NO | NO | NO | Flush | Flush | NO | NO | OK | NO |
| Phosphate | NO | NO | NO | Caution | Caution | NO | NO | NO | OK |
Rules of thumb
- PAG never mixes. Turns into gel with mineral or PAO. Full flush + seal check.
- Silicone stays alone. Very low surface tension — cross-contamination kills lubricity of most other fluids.
- Food-grade (H1) is one-way. Once you contaminate with non-H1, the sump loses H1 certification until fully flushed.
- Elastomers matter. PAG, phosphate ester, and ester oils attack NBR (Buna-N) seals — verify seal/hose compatibility with the new fluid.
- Same brand, different family = still incompatible. Base-stock chemistry drives compatibility, not brand or additive package.