Oil & Kerosene Blend Calculator
Calculate the right heating oil / K-1 kerosene blend for cold weather. Protect your system from fuel gelling.
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Why Blend Heating Oil with Kerosene?
#2 heating oil begins to gel around 20°F as wax crystals form in the fuel. This can clog filters and fuel lines, shutting down your heating system. K-1 kerosene has a much lower gel point (approximately -40°F), so blending the two lowers the effective gel point of the fuel in your tank.
Outdoor tanks are especially vulnerable because they lack the insulation of basement installations. If your tank is outside and temperatures regularly drop below 20°F, a kerosene blend is standard practice.
Recommended Blend Ratios by Temperature
| Temperature | Recommended Blend | Gel Point Protection |
|---|---|---|
| Above 20°F | 100% #2 Heating Oil | ~20°F |
| 10°F to 20°F | 80% Oil / 20% Kerosene | ~8°F |
| 0°F to 10°F | 70% Oil / 30% Kerosene | ~2°F |
| -10°F to 0°F | 50% Oil / 50% Kerosene | ~-10°F |
| Below -10°F | 100% K-1 Kerosene | ~-40°F |
How the Gel Point Calculation Works
The effective gel point of a blend is approximately proportional to the mix ratio. #2 oil gels at ~20°F and K-1 kerosene gels at ~-40°F. A 50/50 blend gives a gel point around -10°F. The actual gel point depends on fuel quality and additives, so these are conservative estimates.
Frequently Asked Questions
What is K-1 kerosene?
K-1 (or 1-K) is a refined grade of kerosene with very low sulfur content. It burns cleaner than #2 heating oil and has a gel point around -40°F, making it ideal for blending or for use in outdoor tanks during extreme cold. Most heating oil suppliers in the Northeast also sell K-1 kerosene.
Can I mix kerosene with heating oil myself?
Yes. Many homeowners in cold climates order a kerosene blend delivery or add kerosene to their existing oil tank. The fuels are fully compatible. If adding kerosene to an existing tank of oil, the blend ratio will be approximate based on how much oil is already in the tank.
Why is kerosene more expensive than heating oil?
K-1 kerosene requires additional refining to remove heavier hydrocarbons and reduce the sulfur content. This extra processing typically adds $0.50–$1.00 per gallon. The premium is justified for outdoor tanks or extreme cold where fuel gelling would leave you without heat.
What is the minimum order for kerosene?
Most suppliers require a 100–150 gallon minimum order for delivery, whether oil or kerosene. Some suppliers offer pre-blended fuel (e.g., 80/20 or 70/30) as a standard product during winter months. Call your supplier to ask about blend options.