Can kerosene be substituted for diesel?

Yes, but only in limited, carefully managed situations: kerosene can be blended with diesel—typically up to about 20–30% in modern engines and sometimes higher in older mechanical-injection engines—mainly to improve cold-weather performance, and only if a proper diesel lubricity additive is used. Running straight kerosene in most modern common-rail diesel engines is not recommended due to poor lubricity and lower energy content, which can accelerate fuel-pump and injector wear, reduce power and fuel economy, and create legal or warranty issues. Here’s what to know before you consider it, when it’s acceptable, and when it’s not.

What kerosene and diesel are—and why the difference matters

Kerosene is a lighter, more refined distillate (similar to Jet-A) with lower viscosity and lower lubricity than standard No.2 diesel. In North American fuel standards, “No.1-D” diesel and 1‑K kerosene occupy a similar space, while “No.2-D” is the everyday road diesel most drivers use. Those differences affect how engines run and how well critical components are protected.

The most important technical distinctions are summarized below to set expectations about performance and risk.

• Lubricity and viscosity: Kerosene has significantly lower lubricity than ULSD (ultra-low sulfur diesel). High-pressure common-rail fuel pumps and injectors rely on fuel lubricity; using kerosene straight can increase wear without an additive that meets ASTM D975/HFRR ≤ 520 μm.
• Energy content: Per liter or gallon, kerosene delivers less energy than No.2 diesel (roughly 3–6% lower), which typically reduces power and fuel economy.
• Cold-flow properties: Kerosene resists gelling better than No.2 diesel, which is why it’s blended into “winterized” diesel to improve cold starts and prevent fuel filter plugging.
• Cetane and combustion: Cetane for kerosene is often slightly lower than diesel, which can mean rougher combustion and more noise without the right additive package.
• Flash point and safety: Kerosene’s lower flash point makes it more volatile than No.2 diesel, affecting storage, handling, and transport rules—but it remains far less volatile than gasoline.
• Sulfur and legality: On-road engines require S15 (15 ppm sulfur) fuel. Many kerosenes meet this; dyed heating kerosene often doesn’t and is illegal to use on-road.

In short, kerosene’s lighter profile helps in cold weather but compromises lubricity and energy content, which are crucial to the longevity and performance of modern diesel systems.

Can you use kerosene in a diesel engine?

The nuanced answer depends on your engine type, the kerosene grade, the blend ratio, ambient temperature, and whether you add the right lubricity package. Fuel suppliers routinely winterize diesel with No.1 components (kerosene-like) under ASTM D975; that’s safe. Problems arise when users substitute straight kerosene, use the wrong grade, or skip lubricity additives.

When limited substitution can work

These are the common, generally accepted circumstances in which kerosene can be used judiciously with diesel without undue risk.

• Winterized retail diesel: Buying “winter diesel” already blended with No.1-D by a reputable supplier is the preferred method; it meets specification for lubricity and additives.
• Emergency or extreme cold blending: Adding kerosene up to about 20–30% with a quality diesel lubricity additive is commonly tolerated by modern common-rail engines; older mechanical-injection engines may accept blends up to ~50% in severe cold.
• Approved heaters/boilers: Many diesel-fired heaters (e.g., bunk heaters, hydronic units) and some small generators are rated to run on kerosene or diesel interchangeably.
• Jet fuel equivalents: Jet-A/Jet A-1 is a kerosene-grade fuel; some fleets and militaries run it in diesel engines with appropriate lubricity additives and within OEM limits.

In these scenarios, the key is that either the fuel already meets the diesel spec or you’ve restored lubricity and other properties through correct blending and additives.

When substitution should not be attempted

There are clear cases where kerosene use invites damage, legal exposure, or both.

• Straight kerosene in modern common-rail engines: The low lubricity can rapidly wear high-pressure pumps and injectors.
• Unknown or high-sulfur kerosene: Using 2‑K or dyed heating kerosene in on-road vehicles can harm aftertreatment and is illegal on public roads.
• No lubricity additive: If you can’t properly dose an approved diesel lubricity additive, don’t blend kerosene yourself.
• Extended use under heavy load: Long runs of kerosene-heavy blends increase wear risks and reduce DPF/SCR aftertreatment effectiveness.

If your situation matches any of these, wait for proper diesel or obtain a compliant winter blend from a trusted supplier.

If you must use kerosene: practical steps

When circumstances force a kerosene blend, a careful, methodical approach reduces risk to your fuel system and emissions hardware.

1. Verify the fuel: Prefer No.1-D S15 diesel, 1‑K low-sulfur kerosene, or Jet-A/Jet A-1. Avoid 2‑K or any high-sulfur or dyed heating kerosene for on-road use.
2. Check the owner’s manual: Many OEMs publish maximum kerosene or No.1 blend ratios and require additives; follow engine-specific guidance.
3. Blend conservatively: For modern common-rail engines, keep kerosene to about 20–30% in the tank; older mechanical systems may tolerate up to ~50% in severe cold. Favor pre-mixed winter diesel whenever possible.
4. Restore lubricity: Dose a reputable diesel lubricity additive per label, targeting ASTM D975/HFRR ≤ 520 μm. Choose ashless formulations compatible with DPF/SCR systems.
5. Prime smartly: If you’ve run the tank low, fill the filter with straight diesel, not kerosene, before priming and starting.
6. Operate gently: Avoid high loads and prolonged idling; monitor for hard starts, extra noise, or warning lights. Refill with straight ULSD as soon as it’s available.
7. Aftercare: Replace the fuel filter at the next service interval and check for any stored diagnostic trouble codes related to fuel pressure or combustion.

Following these steps won’t turn kerosene into diesel, but it helps mitigate the primary risks—poor lubricity and altered combustion—until proper fuel is available.

Legal and safety considerations

Beyond mechanical issues, kerosene substitution carries regulatory and handling implications drivers often overlook.

• On-road legality: Only clear, taxed, S15 fuel is legal for highway use. Dyed kerosene or off-road fuel in an on-road vehicle can lead to fines.
• Emissions and warranty: Non-spec fuels can compromise DPF regeneration and SCR function, triggering faults and potentially voiding warranty coverage.
• Storage and handling: Kerosene’s lower flash point demands proper containers and ventilation; keep away from ignition sources.
• Additive choices: Avoid improvised “additives” like motor or 2‑stroke oil; they add ash and can foul aftertreatment. Use products designed for ULSD.

Treat kerosene with the same compliance mindset you use for diesel: meet sulfur limits, pay taxes where required, and protect emissions systems.

Performance and emissions: what to expect

Drivers often notice subtle differences when kerosene is present. Understanding them can prevent misdiagnosis.

• Reduced power and fuel economy: Expect a modest drop in both due to lower energy density.
• Combustion character: Slightly harsher combustion and more noise are possible without cetane-improving additives.
• Cold-start improvement: Blends with kerosene typically crank and run better in subfreezing conditions.
• Aftertreatment behavior: Lower soot can aid DPF loading rates, but reduced exhaust heat and additive mismatches can hinder regeneration if blends are heavy or prolonged.

These effects are normal in the short term; they should vanish once you return to straight ULSD that meets your local seasonal spec.

Bottom line

You can substitute kerosene for a portion of diesel in specific, short-term scenarios—especially for cold-weather protection—provided the fuel is low-sulfur, properly blended, and treated with a suitable lubricity additive. Avoid running straight kerosene in modern common-rail engines, don’t use dyed or high-sulfur kerosene on-road, and follow your OEM’s guidance. When in doubt, buy winterized diesel from a reputable supplier rather than blending at home.

Summary

Kerosene is not a drop-in replacement for diesel, but it can be a controlled, temporary tool: safe as part of a spec-compliant winter blend or a conservative emergency mix with the right additive. The benefits are better cold flow; the tradeoffs are lower lubricity and energy content, plus legal and warranty risks if you pick the wrong product or ratio. For most drivers, the safest path is purchasing winterized diesel that already meets ASTM specifications for your climate.