Grade 1-D diesel, also known as No. 1 diesel fuel oil, is a light, low-viscosity distillate fuel specified under ASTM D975. It is specifically engineered for cold-weather operation, high-speed diesel engines, and applications requiring reliable fuel flow and rapid ignition at low temperatures.
Compared to Grade 2-D diesel, Grade 1-D contains shorter hydrocarbon chains, lower wax content, and higher volatility, making it ideal for sub-zero and winter-dominant environments.
Chemical & Physical Composition
Primarily C9–C16 hydrocarbons
Reduced wax paraffinic hydrocarbons
Naphthenic hydrocarbons
Limited aromatics for cleaner combustion
Additives for lubricity, corrosion inhibition, and stability
Key Technical Properties
| Property | Typical Range |
|---|---|
| Viscosity @ 40°C | 1.3 – 2.4 cSt |
| Cetane Number | 40 – 55 |
| Flash Point | Lower than Grade 2-D |
| Cloud Point | Very Low |
| Pour Point | Very Low |
| Sulfur Content | ≤ 15 ppm (ULSD) |
| Wax Content | Minimal |
Performance Characteristics
Superior Cold-Weather Operability: Prevents fuel gelling, filter plugging, and injector starvation
High Volatility: Faster vaporization and improved cold starts
Lower Viscosity: Better spray atomization and reduced injector wear
Cleaner Combustion: Lower particulate formation and carbon deposits
Refining & Production Process
Atmospheric distillation (light distillate cuts)
Hydrotreating to remove sulfur, nitrogen, and aromatics
Wax control and cold-flow optimization
ULSD compliance for emission standards
Applications
Extreme cold climates (Canada, Northern Europe, high altitudes)
Winter diesel blending with Grade 2-D
High-speed diesel engines
Emergency generators and backup power
Military, remote, mining, and construction equipment
Comparison: Grade 1-D vs Grade 2-D
| Feature | Grade 1-D | Grade 2-D |
|---|---|---|
| Cold Flow | Excellent | Moderate |
| Viscosity | Lower | Higher |
| Energy Content | Slightly Lower | Higher |
| Wax Content | Very Low | Higher |
| Cost | Higher | Lower |
Advantages
Reliable cold-weather performance
Reduced fuel system blockage risk
Cleaner combustion and lower deposits
Improved starting in sub-zero conditions
Limitations
Lower energy density than Grade 2-D
Higher refining and supply cost
Reduced lubricity (additives recommended)
Not economical for warm climates unless blended
Regulatory Compliance
ASTM D975 (USA)
EN 590 (Europe – blended equivalents)
ULSD emission standards
Compatible with modern diesel engines with lubricity additives