No, you should not mix different types of burning oil. Mixing oils with different viscosities, additives, or fuel types (such as kerosene, diesel, or waste motor oil) can cause improper combustion, increased emissions, and damage to your burner or engine. For heating applications, always use the oil specified by the manufacturer. For engines, stick to the recommended oil grade and type.
Why Mixing Burning Oils Is Risky
Different burning oils have distinct chemical properties. Kerosene burns cleaner and hotter than diesel, while waste motor oil contains contaminants that can clog nozzles and filters. Mixing them alters the flash point, viscosity, and energy content. This can lead to incomplete combustion, soot buildup, and even dangerous flare-ups. In home heating systems, using unapproved blends may void warranties and create carbon monoxide hazards. For engines, mixing oil types (e.g., conventional and synthetic) is generally safe if they share the same viscosity, but mixing different fuel oils is not.
Specific Scenarios and Honest Caveats
Mixing Kerosene and Diesel in Heaters
Some users mix kerosene with diesel to reduce cost or improve cold-weather performance. While a small amount of kerosene (up to 10%) can improve diesel flow in freezing temperatures, exceeding this ratio can lower lubricity and damage fuel pumps. In kerosene heaters, adding diesel increases soot and odor. Always check your heater’s manual; many prohibit diesel entirely.
Mixing Waste Motor Oil with Heating Oil
Waste motor oil is sometimes burned in specialized furnaces, but mixing it with standard heating oil is not recommended. Motor oil contains heavy metals and additives that produce toxic ash and emissions. This practice is illegal in many areas without proper permits. Even in approved waste oil burners, blending with other oils can upset the combustion balance and increase maintenance.
Mixing Conventional and Synthetic Engine Oil
For engines, mixing conventional and synthetic oil of the same viscosity (e.g., 5W-30) is generally safe and will not cause immediate damage. However, the performance benefits of synthetic oil (better protection, longer intervals) are diluted. If you must top off, use the same type and brand if possible. Avoid mixing different viscosities (e.g., 10W-30 with 5W-20) as this can alter oil pressure and flow.
Frequently Asked Questions
Can I mix kerosene and diesel in my home heater?
Only if your heater is rated for diesel blends. Most kerosene heaters are designed for pure kerosene. Adding diesel can cause excessive soot, clogged wicks, and potential fire hazards. Check your owner’s manual before attempting any mix.
Is it safe to mix synthetic and conventional oil?
Yes, it is safe in an emergency. Modern oils are compatible, but mixing reduces the synthetic’s advantages. For long-term use, stick to one type. If you must mix, ensure both have the same viscosity rating and meet your engine’s specifications.
What happens if I mix waste oil with heating oil?
Mixing waste oil with heating oil is not recommended. It can produce harmful emissions, damage your burner, and may violate environmental regulations. Use only approved fuels for your heating system.
The Bottom Line
Mixing different types of burning oil is generally unsafe and can lead to equipment damage, increased emissions, and safety risks. Always follow the manufacturer’s fuel recommendations. For engines, mixing oil types is acceptable in a pinch, but for burners and heaters, avoid blending unless explicitly allowed. For more on engine oil maintenance, check out our guide on best engine oil and engine oil tips.
More Engine Oil Guides
- Does Cold Weather Affect Burning Oil? Here’s What You Need to Know
- Burning Oil Myths Mechanics Wish You Knew
- What Happens if You Neglect Oil Additives?
- What Diesel Engine Oil Tells You About Engine Health
- Does Cold Weather Affect Diesel Engine Oil? What You Need to Know
- Diesel Engine Oil Myths Mechanics Wish You Knew
Video Guide
Video: Related tutorial from YouTube