Can You Put Diesel In An Oil Furnace?

As the winter months set upon us, many homeowners turn to their oil furnaces to help keep them warm. But what can you do when you're running low on oil and unable to fill your furnace as intended? Are there options for a temporary fuel fix that will keep you warm in the interim, like diesel, for example? We here at have researched this question for you and answered it down below.

As it is sold at gas stations, diesel makes an acceptable substitute for home heating oil in almost all heating furnaces. Diesel and heating oil No. 2 are midweight distillations of petroleum that produce roughly the same amount of heat and can be burned by the same systems. This fact makes diesel an acceptable stopgap in a pinch. 

There are more details to go into when it comes to oil heating furnaces and the potential use of diesel. Continue reading as we delve into more about why this fuel can work for you down below.

Man filling a bunded oil tank with domestic heating oil (kerosene) at a home. Can You Put Diesel In An Oil Furnace

Is diesel fuel the same as home heating oil?

Diesel will make an acceptable stopgap between fills of your oil furnace because it burns similarly to the oil used to heat homes. However, it is crucial to recognize that using diesel is only a good idea for the short term.

Diesel is not helpful as a permanent replacement for heating oil in your furnace. Attempts at long-term use will eventually interfere with the functionality of the furnace.

Diesel burns slightly hotter than heating oil, which will do damage to your furnace parts if used for too long. Recognize diesel as the temporary stopgap it is meant to be.

Do note that diesel only works as an acceptable replacement for heating oil No. 2. The No. 2 refers to the weight and grade of the oil, and almost all home oil furnaces use this grade of heating oil. If, for some reason, you use a different quality of oil in your heating furnace, diesel likely won't work for you. Check beforehand to make sure the oil grade your furnace is using is heating oil No. 2.

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Can I use off-road diesel in my oil furnace?

Off-road diesels are dyed red types that show that it is untaxed and available for off-road fuel uses. These uses include construction fueling, equipment never used on public roading, agricultural service, and heating oil boiler fuel. But can these forms of diesel fuel be used in your home furnace to heat your house?

Man filling oil tank with domestic heating kerosene

The answer is generally yes; dyed and off-road diesel is an acceptable alternative to heating oil. Dyed and off-road diesel are typically ultra-low-sulfur diesel these days.

Heating oil can be either low sulfur or high sulfur, according to EPA and most state laws. This means that while heating oil sometimes cannot be dyed diesel (when used for off-road equipment or agricultural use), dyed or off-road diesel can be used as a substitute for heating oil.

How do you pour diesel into an oil tank?

The man wears gloves and fastens a hose for fuel oil delivery

As mentioned above, there are specific ways to pour diesel into your oil tank to avoid causing trouble. There is no limit to the amount of diesel you can use at once when filling your tank, so long as you don't plan to use it as a long-term solution. Use the following steps to add diesel into your heating oil tank safely.

  • You will first need a container that can hold at least ten gallons of diesel fuel. Choose a yellow container that signifies diesel to differentiate it from any other fuels you may have stored at your home.
  • Go to your local gas station and acquire the fuel. Purchase five to ten gallons, depending on how much you think you'll need to last until you get more heating oil.
  • Shut your furnace off before adding any fuel to it.
  • Go to the oil tank's fill pipe at the exterior of the house. Remove the cap and pour the fuel into the fill pipe, which leads directly into the gas tank.
  • Wait ten minutes before turning the furnace back on. Doing so allows any sediment that might have gotten stirred up to settle back down. Once the residue has rested at the bottom, only clean fuel should go through the pipes upon startup, and your system should be safe from clogging.
  • In the unfortunate case that your system has suffered from any clogging or sludge intake, you'll need to likely call in an expert to clear out the oil filter or the fuel oil lines.
  • Turn your heating system back on and resume regular use.

What determines the prices of heating oil and diesel?

You might be noticing the difference between purchasing diesel versus purchasing home heating oil in the exact quantities. This is even the case when diesel is subject to government taxes that home heating oil isn't.

The primary determinant of both fuel costs is the cost of crude oil at any given time. In many ways, heating oils and diesel fuels are fairly similar fuels and this is shown in the ways they are similarly priced.

Yellow plastic gallon for diesel fuel bulk buying

There are, however, specific costs to each of these fuels that can drive one up compared to the other at a given instance. Diesel is made to pass intense sulfur standards that heating oil doesn't have to deal with, which frequently drives up its cost. There are also several taxes levied specifically on diesel in the United States that other fuel sources don't have to deal with.

Delivery costs are something heating oils have to deal with that diesel does not. While you can simply go to your local gas station and pick up diesel, heating oil requires delivery. To further compound this cost, the trucks that deliver heating oil are much smaller than diesel trucks. This leads to less fuel delivered per truck.

These are all considerations that show up in the cost of the oils. While the similarities of the product themselves are numerous, the differences in how they are handled do make an impact on the cost. Keep in mind that while diesel may at times seem like a cheap alternative, it will lead to damages down the road that will cost to repair.

How long will 5 gallons of diesel last in an oil tank?The man wears gloves and fastens a hose for fuel oil delivery

The question of how long fuel will last you depends on factors like how warm you want your home and how big your home is. In general, however, five to ten gallons of diesel or kerosene will last you around one to two days. Keep this in mind when deciding how much diesel to purchase to cover until your next shipment of heating oil.

If you have a more spacious house, consider getting more on the upside of ten gallons of diesel. This will ensure that your home stays comfy until your next delivery arrives.

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Notes on using other fuels in your home furnace

Kerosene is another acceptable replacement for heating oil in the short term. Gasoline, however, is not. Gasoline is a lightweight distillation that will cause damage and other operating issues to your furnace if placed within. Don't try to use regular gasoline in your furnace for any length of time under any circumstances.

If you are going to store diesel in your home for heater use, take the following precautions. Store the fuel in the properly colored container, yellow, and label it clearly.

Avoid keeping your diesel for more than six months, as it will begin to degrade and potentially become dangerous. You can add an additive to your diesel to prolong its shelf life. You will need to use the treated fuel within a year or discard it.

One final note is that the diesel-furnace oil substitution only goes one way. That is, heating furnace oil does not replace diesel fuel for vehicles. It lacks the lubrication needed to keep an engine running properly without incurring damage or being potentially dangerous.

Man holds a yellow plastic jerrican for diesel fuel in his hand on a black background. Can You Put Diesel In An Oil Furnace

In Closing

Diesel is an acceptable stopgap for when you've run low on heating oil to keep your home comfortable and warm. As long as you're aware of its limitations and what it's capable of, it'll be a great temporary solution to an unfortunate problem. We hope this guide has helped you realize what diesel can do for you as an oil heater user. May you be safe and comfortable for many years to come.

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  1. Thank you for explaining that five to ten gallons of diesel can last you about one or two days of heating. My friend has been wondering what fuel she can use to hold her over until her next shipment arrives on Monday. I’ll be sure to mention this to her so that she can try getting some diesel to hold her over for the weekend.

    • BTW some gas stations also sell #2 home heating oil. Often the pump for #2 oil (and Kero, racing fuel, and other specialty fuels) is located near the building, not out with the gas pumps. Buying tax-free #2 oil if you can find it, will be cheaper than buying on-road diesel.

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