Diesel engines and the technical implications of using heating oil

While heating oil and road diesel are both refined from crude oil and share similar chemical compositions, they possess distinct properties that affect vehicle performance. A key difference is the cetane number; heating oil has a lower cetane rating (approximately 40 to 41) compared to diesel (approximately 51), making it less flammable and less suitable for engine combustion.

Technically, using heating oil in older diesel engines may not cause immediate damage, but it is not designed for modern automotive engines. Heating oil contains significantly higher sulfur levels—up to 1,000 ppm—compared to road diesel. This discrepancy can lead to incomplete combustion, resulting in increased smoke, deposits, and unburnt fuel. Over time, these residues can clog fuel filters, injectors, and high-pressure pumps, while also accelerating wear on catalytic converters and particulate filters.