Excerpt from Amazon Hose website (not Amazon.com)
Diesel Fuel Hose: Rating Systems
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diesel fuel hose can be used for a number of marine and fuel extraction purposes. To maintain safety and quality standards, diesel fuel hoses are rated for specific applications using a combination of a number and a letter.
The US Coast Guard (USCG) has rated four types of diesel fuel hoses, A1, A2, B1 and B2. According to the USCG recommendations, all marine applications must use the Type B hose at fuel pump and carburetor sections of the fuel line system. A leakage at these sections can cause huge loss of fuel. Also, the Type B diesel hose is fire resistant, minimizing the risk of a fire outbreak. The USCG also recommends the Type 1 hose for critical applications due to their low permeation characteristic. Coast Guard standards require all fuel hoses used for marine applications to bear the mark USCG every 12 inches, while specifying the manufacturing date.
The American Boat & Yacht Council (ABYC) recommends the Type B1 fuel hose for diesel-based applications. The Type A1 hose is the best option for gasoline supply. This hose is less permeable, highly durable, heat resistant and does not collapse under high pressure or vacuum.
Petroleum products have a huge wear and tear effect on fuel hoses. Thus, it is essential to buy high quality hoses to ensure long-term results. However, one should check fuel hoses for cracks, rot or sponginess every quarter. According to the USCG standards, fuel hoses should be wiped with a dry rag and checked for fuel odor.