The Differences in Propane Grades

HD-5 grade propane is “consumer grade” propane and is the most widely sold and distributed grade of propane in the U.S. market. HD-5 is the highest grade propane available to consumers in the United States and is what propane companies ordinarily sell to their customers. This is the type of propane we sell for local residential and commercial use. What does HD-5 propane mean in terms of specification to an ordinary consumer? It means that the propane is suitable and recommended for engine fuel use, which was the original purpose of the HD-5 grade propane specification. HD-5 spec propane consists of:

• Minimum of 90% propane
• A maximum of 5% propylene-propylene is used in the manufacture of plastics
• Other gases constitute the remainder (iso-butane, butane, methane, etc.)

The HD-5 specification is based on “allowable” content. For instance, 99% propane and 1% propylene is HD-5 grade propane the same as 95% propane and 5% propylene is HD-5 propane. Although the product consistency and purity are different, both mixtures are considered HD-5 propane because they fall within the allowable limits for the product to be named and labeled as such. Consider this: 10,000 gallons of pure propane (100% propane) is classified as HD-5 grade propane.

Retail propane companies that advertise “highest quality propane” are actually selling propane that conforms to the specifications as required to be labeled and sold as HD-5 propane. An important fact to note is that there is no higher grade than HD-5 propane available for resale through retail propane companies in the United States…HD-5 is the highest-grade propane available to U.S. consumers. A company stating that their propane is of a higher grade than HD-5 is inaccurate in their claim. As presented above, a tank holding pure propane contains what is classified as HD-5 propane.

HD10 propane is a grade below HD-5 and is commonly found in California. HD-10 grade propane allows up to 10% propylene in the propane/propylene mixture and is still labeled as “propane”. Because propylene is used in creating plastics, HD-10 can possibly create problems in some engines and vehicle applications. Propylene can cause engine components to “gum” or stick during operation. However, HD-10 spec propane works just fine in domestic and commercial propane-powered appliances. The primary problem that may be encountered in using HD-10 propane involves its use as an engine fuel (vehicles, forklifts, etc.).

Commercial grade propane and HD-10 grade propane are sometimes used interchangeably due to the fact that both grades are sub-HD-5 spec products and do not meet the standards of engine-grade propane. Refineries use commercial propane in their processes and the fractionation of chemicals for end use in numerous industries. Although commercial-grade propane can be used in a manner similar to that of HD-10 propane, it is not used in vehicle applications. We currently do not sell HD-10 propane.