Using Biodiesel in Generators: Why Fuel Quality Matters

The fuel you put into your diesel engine is more than just a power source—it plays a critical role in engine performance, reliability, emissions, and maintenance. Poor-quality fuel can lead to hard starts, increased smoke, injector fouling, component wear, and even premature engine failure. At Aurora Generators, we emphasize the importance of using fuel that meets the manufacturer’s specifications to ensure maximum performance and longevity of your equipment.

The Role of Fuel in Engine Health

Diesel engines are engineered with tight tolerances and advanced fuel systems, particularly those equipped with emissions aftertreatment like DPFs and DOCs. As such, fuel that doesn’t meet key quality parameters can have a significant impact on:

• Cold starting
• Power output
• Fuel system wear
• Exhaust emissions
• Maintenance intervals
• Warranty coverage

Key Diesel Fuel Properties to Monitor

1. Cetane Number

Cetane rating indicates how quickly fuel ignites under pressure. A higher cetane number (≥ 45 in Europe, ≥ 40 in North America) reduces ignition delay, making cold starts easier. Fuels with low cetane can increase combustion noise, emissions, and misfires.

2. Viscosity

Fuel acts as a lubricant in modern diesel engines. Viscosity that is too low may lead to fuel pump and injector damage; too high, and it can cause poor atomization and filter blockage. The recommended range is 1.4–4.5 cSt at the injection pump.

3. Density / Specific Gravity

This determines energy content. Higher density fuels deliver more power but may increase smoke. Lower-density fuels reduce power output. Perkins engines, for example, recommend a density near 841 kg/m³ for rated power.

4. Sulfur Content

High sulfur content damages aftertreatment devices and increases internal corrosion. For emissions compliance:

• ULSD must be ≤ 15 ppm in the U.S.
• Stage V diesel in Europe requires ≤ 10 ppm.

Avoid blending used oils into diesel, as this raises sulfur and contaminant levels beyond acceptable thresholds.

5. Lubricity

Measured by the HFRR wear scar test, acceptable diesel fuel should leave a scar ≤ 0.52 mm. Poor lubricity shortens the life of fuel pumps and injectors. Use additives cautiously and consult with your supplier first.

6. Volatility and Distillation

Fuel volatility affects combustion and engine warm-up. Fuels that are too volatile may evaporate too quickly, while low volatility fuels can lead to poor cold starts or crankcase oil dilution—especially in biodiesel blends.

7. Oxidative Stability

Biodiesel degrades faster than petroleum diesel, especially under heat. It forms acids, gums, and varnishes, which clog filters and damage injectors. Ensure biodiesel meets minimum oxidation stability requirements.

8. Cleanliness

Fuel must meet ISO 18/16/13 or cleaner to protect injectors and pumps. Always filter fuel down to 4 microns absolute or less. Inspect for water, sediment, or visible contaminants.

9. Cold Flow Properties

Watch the cloud point, pour point, and CFPP when operating in cold climates. Wax in diesel can solidify and clog fuel lines. Use heaters or cold-flow improvers as needed.

Fuel Types: What’s Approved and What’s Not

✅ Recommended

• Distillate Diesel Fuels: ASTM D975 No. 1-D or 2-D, EN590.
• ULSD: Required for engines with emissions aftertreatment.
• Renewable Diesel (HVO): Drop-in replacement, compatible with most systems.
• Biodiesel Blends: B7 to B20 in many engines. Monitor oil condition regularly.

⚠️ Use with Caution

• Jet Fuels (Jet A, JP-8): Emergency use only. Reduced power and lubricity.
• High Biodiesel Blends (B35–B40): Use where allowed and monitor filters/oil.

❌ Not Approved

• Raw Vegetable Oils
• Heavy Fuel Oils or Residual Fuels
• Used Motor Oils as Fuel Blends

Best Practices to Protect Your Generator

• Use only fuel that meets OEM specifications.
• Store diesel in clean, water-free containers and tanks.
• Use fuel additives only when recommended by the engine or fuel supplier.
• Filter fuel at both bulk storage and point of dispensing.
• Monitor oil quality when using biodiesel or alternative fuels.
• Keep records of fuel source and analysis to help with warranty and diagnostics.

Final Thoughts

Fuel quality is not optional—it’s essential. Whether you operate a residential standby system or a critical commercial generator, the wrong fuel can quickly lead to costly downtime and repairs. At Aurora Generators, we recommend working with trusted fuel suppliers, following proper storage and filtration practices, and always consulting your engine manual for fuel compatibility.

Need help choosing the right fuel or filtration setup? Contact us—we’re here to help.