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.
How to use this calculator
Check whether two lubricant chemistries can be mixed or require a full flush.
- Select the lubricant currently in the machine.
- Select the lubricant you intend to add.
- Read the compatibility verdict and any flush requirement.
- Follow the stated seal and filter cautions before topping up.
Frequently asked questions
- Can you mix different compressor oils?
- Only within compatible chemistries. Mixing polyglycol (PAG) with PAO or mineral oil forms sludge and varnish, and diester fluids can attack seals meant for mineral oil.
- Do I have to flush when changing lubricant types?
- Yes for incompatible chemistries: drain hot, change the separator and filters, flush with the new fluid, run briefly, then drain and refill.
- Will synthetic oil leak in an older compressor?
- Some synthetics clean deposits that were plugging marginal seals, so pre-existing leaks show up after the change. Replace suspect seals when converting.