Grades of Propane – Gas Purity and Quality

grades of propane

Propane is propane regardless of the grade. However, there are three grades of propane. Each of the three grades, HD5, HD10 and commercial propane differ in propane consistency and all have different purposes. All grades of propane come from the same raw materials (crude oil or natural gas). The creation of differing grades of propane is during the refining or processing of the gas at the refinery. Simply put, the refinery specifies which grade to process. Each propane grade is stored separately following processing. This is to ensure that when loading, the refinery matches what the buyer needs.

Different Grades of Propane

HD-5 Propane

HD5 grade propane is “consumer grade” propane. It is the most common and the highest grade propane available to consumers in the U.S. This grade propane is what we often sell to our customers. HD5 means that the propane is suitable for engine fuel use, which was the original purpose of the propane grade specification.

HD5 spec propane consists of:

  • Minimum of 90% propane
  • Maximum of 5% propylene – manufacturing plastics requires propylene
  • Other gases constitute the remainder (iso-butane, butane, methane, etc.)

The HD5 specification depends on “allowable” contents. For example, 99% propane and 1% propylene is HD5 grade propane the same as 95% propane and 5% propylene is HD5 propane. The product consistency and purity is different, but both mixtures are HD5 propane because they fall within the allowable limits for the product to have the name and label as such. Consider this: 10,000 gallons of pure propane (100% propane) is classified as HD-5 grade propane.

When advertising “highest quality propane”, this actually means that the propane conforms to the specification requirements to label and sell as HD5 propane. An important fact to note is that there is no higher grade than HD5 propane available in the U.S. HD5 is the highest grade propane available to U.S. consumers.

Therefore, any propane company stating their propane is of a higher grade than HD4 is inaccurate in their claim. As mentioned above, a tank holding pure propane contains what is classified as HD5 propane.

HD-10 Propane

HD10 grade propane allows up to 10% propylene in the propane/propylene mixture and is still has a “propane” label. Creating plastics uses propylene, so HD10 can possibly create issues in some engines and vehicle applications.

While propylene can cause engine components to “gum” or stick during operation, HD10 spec propane works just fine in domestic and commercial propane powered appliances. The only possible issue in using HD-10 propane involves its use as an engine fuel (vehicles, forklifts, etc.).

Commercial Propane

Commercial grade propane and HD10 grade propane are sometimes used interchangeably. This is due to the fact that both grades are sub-HD5 spec product and do not meet the standards of engine grade propane. Refineries use commercial propane in their processes and fractionation of chemicals for end use in numerous industries. While commercial grade propane can be used in a manner similar to that of HD10 propane, it is not used in vehicle applications.


For more information on propane grades or to schedule your propane delivery with us, contact us with the link below!

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