USA: Fuels: Certification Fuels

Introduction

Properties of fuels required to be used during emission measurement procedures are specified in the emission test procedures relevant to the particular application. At the US federal level, these are found in 40 CFR § 1065 for most applications. Previously, they were included with emission standards in the relevant part of 40 CFR.

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Historically, these fuels were referred to as certification fuels. More recently, they are usually referred to as test fuels.

Part 1065 Test Fuels

Starting in 2004, the EPA finalized rules that moved testing requirements, and thus test fuel specifications for heavy-duty diesel engines, to section 40 CFR § 1065. Rules applying these procedures to Tier 4 nonroad engines were finalized in 2004, to 2010 and later on road engines in 2005 and to Tier 3 and 4 locomotive and marine engines in 2008 [2786][6245][3562].

Table 1 summarizes the properties of three diesel test fuels specified in 40 CFR § 1065. The three fuels are differentiated only by their sulfur content. The ultra low sulfur grade is required for most heavy-duty applications including Tier 4 nonroad engines, 2010 and later on road engines and Tier 4 locomotive and marine engines. While § 1065 ULSD can be used for certification in California, the California test fuel found in Table 2 can also be used.

The primary difference between the ULSD in Table 1 and the 2007-2009 fuel in Table 2 is the maximum aromatic content.

Except for the sulfur level in high sulfur test fuel, the values in Table 1 have remained unchanged since 2004. However, revisions are occasionally made. One such revision occurred in 2014 with the final Tier 3 regulatory package [2999].

In addition to diesel fuel, 40 CFR § 1065 also includes specifications for other test fuels including E10 gasoline, E0 gasoline, E85, natural gas, LPG and residual fuel.

By reference, § 1065 fuels are also applicable to vehicles subject to the vehicle test procedures of § 1066. This includes MY 2014 and later heavy-duty vehicles subject to Phase 2 GHG regulations and all MY 2022 and later light- and heavy-duty vehicles previously subject to test procedures in § 86.

2007 Model Year Vehicles

The EPA 2007-2010 emission standard regulation for heavy-duty highway engines introduced a sulfur limit of 15 ppm. Accordingly, the specifications for emission test fuels were changed as shown in Table 2. The basic certification fuel was the grade 2-D diesel. Grade 1-D was allowed only if the engine manufacturer demonstrated that this fuel would be the predominant in-use fuel. Details are found in 40 CFR § 86.1313–2007 [1044]. The EPA requirements in Table 2 applied to 2007 to 2009 heavy-duty diesel engines. As already discussed, 2010 and later federal heavy-duty engines require the use of ultra low sulfur fuel from Table 1.

California allows the test fuel specifications found in the California Exhaust Emission Standards and Test Procedures for 2004 and Subsequent Model Heavy‑Duty Diesel Engines and Vehicles to be used, Table 2 [5726]. For California, these values apply also to 2010 and later heavy-duty engines.

Regarding the nitrogen content range for California certification fuels, 100 to 500 ppmw was typical of commercial low sulfur values in the 1990s [6250]. Values for ULSD appear to be around 50 ppmw [6251].