Mazut M100: Heavy Fuel Oil Specifications and Common Scams

What Mazut M100 actually is

Mazut M100 is a heavy fuel oil graded under the Russian/CIS GOST 10585 standard. It is essentially the residual oil left after distillation of lighter products from crude. Used in industrial heating, marine fuel blending, and power generation in markets that accept high-sulfur fuel.

The spec under GOST 10585

• Density at 20°C: 0.99 g/cm³ (approximate)
• Viscosity at 100°C: ≤50 cSt
• Sulfur: graded as "very low sulfur" (≤0.5%), "low sulfur" (≤1.5%), or "high sulfur" (≤3.5%)
• Flash point: ≥110°C (closed cup)
• Pour point: ≤25°C

Why M100 offers are usually fraudulent

Russian-origin Mazut faces sanctions exposure in most Western jurisdictions. Despite this, broker chains continue to circulate "M100" offers at impossible discounts to legitimate heavy-fuel pricing.

The pattern:

• Offer comes from a "mandate" with no named refinery
• Discount is 30–50% to Platts heavy fuel oil
• Loading port is vague (often Rotterdam or Fujairah, with no terminal name)
• Documents include obvious GOST template language with no batch numbers

What real M100 looks like

Legitimate heavy fuel oil trade exists, but it is small, opaque, and dominated by handful of trading houses with deep Russian and Central Asian relationships. A walk-in buyer cannot access it — and certainly not at a discount.

What we recommend

If you need heavy fuel oil for legitimate industrial use, contract for IFO 380 / VLSFO under ISO 8217 instead. Same fuel category, internationally recognized specification, multiple non-sanctioned sources, much smaller fraud surface.