How to Read a Re-Refined Base Oil COA: 7 Parameters That Separate Real Group II from Repackaged Waste Oil
Every re-refined base oil supplier will tell you their product "meets Group II specifications." The certificate of analysis is where that claim either holds or collapses. Because the re-refined market spans everything from world-class hydrotreated plants to clay-treatment operations selling barely-processed used oil, the COA is the single most important document in an RRBO purchase — and knowing how to read it is a genuine commercial skill.
Here are the seven parameters that matter, and what each one tells you about what actually happened inside the re-refinery.
1. Saturates content (ASTM D2007)
API Group II requires saturates of 90% or higher. This number is the clearest fingerprint of proper hydrotreating — the process that converts unstable aromatic molecules into stable saturates. A COA showing saturates in the low 80s or missing this line entirely usually means the product was distilled but never hydrotreated. It may still have legitimate uses, but it is not Group II and should not be priced as Group II.
2. Sulphur (ASTM D4294 or D5453)
Group II requires sulphur below 0.03%. Used oil feedstock arrives with sulphur from fuel dilution and additive residue; only high-pressure hydrotreating strips it out. Elevated sulphur is the fastest way to spot under-processed material.
3. Viscosity index (ASTM D2270)
Expect 95–120 for a genuine Group II re-refined product. VI below 90 suggests either poor feedstock segregation or a distillation-only process. VI also drives how the oil performs across temperature range in the finished blend, so this is a formulation parameter, not just a classification one.
4. Colour (ASTM D1500)
Properly hydrotreated RRBO is water-white to pale yellow — typically 0.5 to 1.5 on the ASTM scale. Darker colour indicates residual aromatics and polar compounds that hydrotreating should have removed. Colour is not a performance property in itself, but it is an honest visual proxy for processing depth, which is why under-processed sellers avoid reporting it.
5. Noack volatility (ASTM D5800) — for lighter grades
For SN150-equivalent grades destined for engine oil or other high-temperature applications, Noack volatility tells you how much of the oil evaporates in service. Poorly fractionated re-refined product often carries light ends that push Noack above acceptable limits, causing oil consumption problems in the finished lubricant.
6. Pour point and flash point
Flash point confirms fuel contaminants were fully stripped during pre-treatment — a low flash point means diesel or gasoline residue survived the process, which is both a performance and a safety problem. Pour point confirms the cut is what the grade name claims.
7. Batch number and test date
The quiet tell. A genuine COA is tied to a specific production batch with a recent test date. A "typical properties" sheet with no batch reference is marketing, not analysis. Serious suppliers provide batch-specific COAs as standard, and can show consistency across multiple batches — because one good batch proves a sample, while a run of consistent batches proves a plant.
What to do with this checklist
Before committing to any RRBO cargo, request the batch-specific COA and check it against these seven lines. If a supplier hesitates, substitutes typical properties, or cannot explain their processing route, the discount they are offering is not a discount — it is the market pricing in exactly the risk you would be taking.
For buyers blending toward EU-destined applications, add one more request: IP 346 polycyclic aromatics data, confirming REACH Annex XVII compliance below 3% PCA. For the regulatory backdrop shaping how re-refined material is collected and processed in Malaysia, see our piece on Malaysia's used oil regulatory framework.
Sanyang Petroleum supplies re-refined and virgin base oils across Southeast and South Asia, with batch-specific documentation as standard. To discuss specifications and current availability, contact our trading desk at info@sanyangpetroleum.com.
Frequently Asked Questions
What saturates level qualifies a base oil as API Group II?
API Group II requires saturates of at least 90% (ASTM D2007). Saturates in the low 80s or lower typically indicate the material was distilled but not properly hydrotreated, in which case it should not be sold or priced as Group II.
Why does the sulphur value on an RRBO COA matter so much?
Group II sulphur must be below 0.03% (ASTM D4294 or D5453). Used oil feedstock arrives high in sulphur from fuel dilution and additive residue, and only high-pressure hydrotreating strips it out. Elevated sulphur is the fastest way to spot under-processed re-refined material.
What is the difference between a batch-specific COA and a typical properties sheet?
A batch-specific COA is tied to a named production batch with a recent test date and lab signature — it certifies the actual material being shipped. A 'typical properties' sheet describes what the product usually looks like and is marketing, not analysis. Serious re-refiners issue batch COAs as standard.
Do I need IP 346 data for RRBO going into EU-destined lubricants?
Yes. For material blended into products destined for the EU, request IP 346 polycyclic aromatics data confirming REACH Annex XVII compliance below 3% PCA. It's an additional line item beyond the seven core Group II parameters but essential for regulatory acceptance.
Evaluating an RRBO supplier right now?
Sanyang Petroleum supplies SANYANG REBASE-150 with batch-specific COAs and traceable Malaysian sourcing. Request a sample or the latest batch documentation from our trading desk.