How is Home Heating Oil Made?

At Heatable, we’re a bunch of New Englanders who have been working in the heating oil business for … well, let’s just say a while… so it will come as no surprise that in that time, we’ve learned a thing or two about heating oil. One of the questions we get asked is how is heating oil made? Well, about that…

The origins of heating oil go back millions of years

Believe it or not, the story of heating oil begins millions of years ago with algae and plants that lived in large and shallow seas. When the algae and plants died, they sank to the bottom of the seafloor where they mixed with other sediment. Year after year the material built up as more algae and plants died and mixed with more sediment. After millions of years, pressure from all that weight and temperature built up until the plant matter was transformed into…wait for it… crude oil (as well as other fossil fuels such as coal and natural gas that don’t happen to be part of this particular story).

Today, that crude oil (or petroleum) is found in the remains of those ancient seas, which are now huge reservoirs beneath the ground.

What is crude oil?

Crude oil is a liquid mixture of hydrocarbons that remains liquid when brought to the surface.  While it’s usually black or dark brown, it can also be yellowish, reddish, tan, or even greenish. Those different colors are caused by the various chemical compositions in the different supplies of crude oil. The fewer metals or sulfur, the lighter in color crude oil tends to be.

[Fun fact: The Internal Revenue Service (IRS) requires fuels that will not be used in vehicles (i.e. heating oil) to be dyed red for tax purposes! Doing so, exempts fuel like heating oil from federal, state, and local taxes that highway-bound fuels have to pay.]

Unfortunately, crude oil straight out of the ground won’t work in oil-burning furnaces. Crude oil has a variety of impurities in it that first need to be separated out. The process of removing those impurities is called refining.

Distillation is the key to refining

Crude oil contains hundreds of different types of hydrocarbons that need to be separated in order to create anything useful. This is where oil refining comes into play. Every barrel of crude oil (a barrel is 42 gallons) gets distilled into a variety of different products such as gasoline, diesel, jet fuel, and heating oil. In fact, that 42 gallons turns into almost 45 gallons of finished products…#magical. Propane is also derived from the distillation process.

So how does oil refining work? How do you separate out the various hydrocarbons in crude oil?

The most common way is through distillation (yes, the same process used to make moonshine and other alcoholic beverages). Distillation works because each of the hydrocarbons in crude oil have different boiling points. The specific type of distillation used at an oil refinery is called fractional distillation.

In fractional distillation, crude oil is heated with high pressure steam to a super high temperature – and when we say ‘high’, we’re not talking 100 degrees Fahrenheit, we’re talking like… 1112 degrees Fahrenheit—and that’s not a typo.

With that type of heat, all the crude oil boils forming a vapor (gas). The vapor then enters the bottom of a long column, and the column is filled with trays or plates each of which has a bunch of holes in it. Those holes allow the oil vapor to pass through them.

Now here’s the thing: the temperature in the column is hotter at the bottom than it is at the top, so as the vapor rises in the column, it cools down. The oil vapor is made up of various substances, all of which have different boiling points. When a substance in the vapor reaches the height in the column where the temperature is the same as its particular boiling point, then that substance will turn back to a liquid, and the trays will collect it. (Pretty sure this should have been a Bill Nye the Science Guy episode!)

The substance with the highest boiling point will turn to liquid near the bottom of the column (the hotter end), and the substance with the lowest boiling point will reach the top of the column (the cooler end).

Through this process of fractional distillation, hydrocarbons are removed from crude oil and become their own pure substances.

But, there’s more!

So, at this point, the crude oil has been separated into substances (also known as fractions), but most of those fractions still aren’t quite ready for market. Seriously.

The next step is to chemically process those fractions in order to make…still other fractions. That is accomplished by using one of these three processes:

  1. Cracking, which takes larger fractions and literally breaks them into smaller ones.

  2. Unification, which combines smaller fractions to make larger ones.

  3. Alteration, which rearranges the molecules in a fraction to produce a different one.

Still with us? OK, so once the chemical processing is complete, the fractions are then treated to remove impurities like metals, salts, sulfur, and oxygen.

And with the introduction of Ultra Low Sulfur (ULS) heating oil, the oil is also refined to remove sulfur, reducing the sulfur content from 4,000 ppm in traditional oil to 15ppm in ULS heating oil.


And finally, the last step in refining crude oil is to blend the correct components (you now know them as fractions) to create products such as heating oil, jet fuel, lubricating oils—and even chemicals for making plastics.

Boom! That is how heating oil is made. And you thought we were just the guys driving around in the orange trucks.

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