Most shipowners don’t need to be told that bunkers are their biggest expense — they feel it every time they sign off on a fuel invoice. What’s less obvious, especially to people outside day-to-day operations, is how much of a voyage’s risk sits quietly inside the bunker supply chain. A single bad stem can derail a schedule, damage machinery or trigger a dispute that drags on for months.
That’s not hypothetical. According to a global marine fuel quality study, 5.4% of VLSFO samples and 7.9% of MGO samples tested in 2024 were off-spec. And a peer-reviewed analysis of fuel variability explains why: modern bunker fuels — particularly blended VLSFO — aren’t uniform products. Their quality depends heavily on who blended them, what they blended, and how carefully the supplier manages the chain of custody.
So choosing a bunker supplier isn’t about getting the lowest price on the screen. It’s about reducing uncertainty. Here’s how experienced operators evaluate suppliers — often quietly, but always carefully.
1. Pricing Transparency: Not Just the Number at the Bottom
A surprisingly large part of bunker procurement comes down to trust. When a supplier sends an offer, you want to understand what’s behind the number. Is it indexed? Does it include barge fees? Are there port charges tucked into “miscellaneous”?
The suppliers who are consistently clear about how they build their price are the ones shipowners tend to stay with. And for good reason: technical reviews of VLSFO blending practices show that cut-rate stems often correlate with unstable blends, excess sediment or outright contamination.
If you bunker in the Strait of Gibraltar, it’s worth benchmarking your offers against a seasoned bunkering supplier in Gibraltar — a region known for strong oversight and clear pricing structures.
What shipowners look for:
A clean quote, transparent breakdown, and no surprises in the reconfirmation.
2. Credit Terms & Financial Dependability
Bunkering is a credit-heavy business. Some suppliers extend generous terms; others operate conservatively. Neither approach is inherently good or bad — what matters is predictability.
Operationally, a supplier who can offer appropriate credit limits and stable payment terms makes your planning easier. On the flip side, suppliers who constantly shift credit conditions create friction for fleet managers and procurement teams.
Industry reporting, including a bunker quality and dispute analysis, shows that disputes often escalate not because of the fuel itself, but because documentation wasn’t aligned or credit agreements weren’t clear. Good suppliers understand that clarity reduces conflict.
What shipowners look for:
Credit that reflects volume, clear payment timelines and quick dispute resolution.
3. Delivery Reliability: The KPI That Matters More Than People Admit
No one advertises poor delivery performance — but every fleet manager has a mental list of ports and suppliers they avoid because of it. “Bunkers delayed four hours” sounds minor on paper. It isn’t, especially if you’re waiting on a tide window or a narrow terminal slot.
On-time, in-full delivery (OTIF) sounds simple, but it’s the clearest operational KPI a supplier can provide. Ask for it.
Why? Because disruptions tie directly into cost. Industry-wide contamination reports show that ports with recurring water, sediment or cat-fine issues also tend to have higher operational delays due to extra testing or onboard troubleshooting.
Suppliers who volunteer their local risks — congestion patterns, weather delays, barge constraints — are the ones who usually perform best.
What shipowners look for:
Consistent delivery windows, low quantity variance and minimal operational drama.
4. Documentation, Compliance & Traceability
Most bunker disputes aren’t won through argument; they’re won through paperwork. If a supplier’s documentation is sloppy, the shipowner is instantly on the back foot.
Proper documentation includes:
- Clean, MARPOL-compliant BDNs
- Pre-delivery Certificates of Quality (not just after-the-fact reports)
- Contractual references to ISO 8217
- Correct sampling and custody-chain procedures
- Reasonable claim windows
A recurring theme in bunker compliance research is that ambiguity around sampling and COQs is the root cause of most long-running disputes. Meanwhile, technical studies on digital documentation show that e-BDNs and blockchain-backed chains of custody dramatically reduce tampering and speed up settlement.
Suppliers who invest in clean documentation are suppliers who get paid on time — and they know it.
What shipowners look for:
Accuracy, consistency and paperwork that holds up under scrutiny.
5. Fuel Quality Assurance: The Heart of the Entire Relationship
No matter how good a supplier looks on paper, nothing matters if their fuel is unreliable. Quality issues remain one of the biggest operational risks in shipping.
The 2024 global bunker testing review makes this clear: even mainstream fuels show consistent off-spec rates. Add to that the findings from a peer-reviewed LCA and quality variability study, which explains why blended fuels behave unpredictably under different conditions, and you start to understand how much depends on a supplier’s QA process.
Good suppliers:
- Test fuels independently
- Provide COQs before delivery
- Flag compatibility risks
- Assist vessels when fuel handling needs adjustment
- Respond quickly when something goes wrong
Bad suppliers usually do the opposite — slowly.
What shipowners look for:
Suppliers who treat fuel testing as a routine part of operations, not an optional service.
Putting It All Together: A Supplier Scorecard That Actually Works
Most experienced operators use a rough scorecard to evaluate suppliers, even if they never write it down. It usually includes:
- Transparency of pricing
- Reliability of delivery
- Strength and clarity of credit
- Quality and completeness of documentation
- Rigor of quality assurance
- Ability to adapt to future fuels (biofuels, methanol, etc.)
Choosing a bunker supplier isn’t a procurement decision — it’s a risk-management decision. The right partner keeps your schedule intact, protects your machinery, and prevents the kinds of disputes that drain time and attention.
When you find a supplier who ticks most of these boxes, you tend to stick with them. That’s not loyalty — it’s self-preservation.
