Key Differences:
* Sulfur Content: Furnace oil typically has a higher sulfur content than light diesel. This is a major distinction. Higher sulfur means more pollution when burned.
* Cetane Number: Light diesel has a higher cetane number than furnace oil. Cetane number is a measure of a fuel's ignition quality – how readily it ignites in a compression-ignition engine (like a diesel engine). A higher cetane number means easier and more efficient combustion. Furnace oil, with its lower cetane number, is not suitable for use in diesel engines.
* Viscosity: Furnace oil tends to have a higher viscosity than light diesel, meaning it's thicker and less easily flowable at lower temperatures.
* Additives: Light diesel often contains additives to improve its performance in engines (e.g., lubricity, detergents). Furnace oil generally has fewer or different additives tailored for its use in industrial heating systems.
Why one might be preferable over the other:
* Light Diesel: Preferred for use in diesel engines due to its higher cetane number, lower sulfur content (especially ultra-low sulfur diesel), and additives designed for engine performance and longevity. It's cleaner burning than furnace oil. However, it's often more expensive.
* Furnace oil: Preferred for industrial heating applications like boilers and furnaces where a high cetane number isn't necessary. It's often cheaper than light diesel. However, its higher sulfur content makes it less environmentally friendly, and many jurisdictions are phasing it out or heavily regulating its use due to air quality concerns.
In short: Light diesel is preferred for its suitability in diesel engines and cleaner burning properties. Furnace oil is preferred (where still allowed) for its lower cost in industrial heating, despite its environmental drawbacks. The choice depends entirely on the intended application. Using furnace oil in a diesel engine would likely cause damage, and using light diesel in a furnace wouldn't be as economical, though technically possible in some cases.
