Section 1048.501 - How do I run a valid emission test?(a) Use the equipment and procedures for spark-ignition engines in 40 CFR part 1065 to determine whether engines meet the duty-cycle emission standards in § 1048.101(a) and (b) . Measure the emissions of all the pollutants we regulate in § 1048.101 using the sampling procedures specified in 40 CFR part 1065. Measure CO2, N2O, and CH4 as described in § 1048.235 . Use the applicable duty cycles specified in §§ 1048.505 and 1048.510 .(b) Section 1048.515 describes the supplemental procedures for evaluating whether engines meet the field-testing emission standards in § 1048.101(c) .(c) Use the fuels and lubricants specified in 40 CFR part 1065, subpart H, to perform valid tests for all the testing we require in this part, except as noted in § 1048.515 . (1) Use gasoline meeting the specifications described in 40 CFR 1065.710(c) for general testing. For service accumulation, use the test fuel or any commercially available fuel that is representative of the fuel that in-use engines will use.(2) You may alternatively use ethanol-blended fuel meeting the specifications described in 40 CFR 1065.710(b) for general testing without our advance approval. If you use the ethanol-blended fuel for certifying a given engine family, you may also use it for production-line testing or any other testing you perform for that engine family under this part. If you use the ethanol-blended fuel for certifying a given engine family, we may use the ethanol-blended fuel or the specified neat gasoline test fuel with that engine family.(d) In place of the provisions of 40 CFR 1065.405 , you may consider emission levels stable without measurement after 50 hours of engine operation.(e) To test engines for evaporative emissions, use the equipment and procedures specified for testing diurnal emissions as described in 40 CFR 1060.525 , subject to the following provisions:(1) Precondition nonmetal fuel tanks as specified in 40 CFR 1060.520(a) and (b) .(2) For engines equipped with carbon canisters that store fuel vapors that will be purged for combustion in the engine, precondition the canister as specified in 40 CFR 86.132-96(h) and then operate the engine for 60 minutes over repeat runs of the duty cycle specified in appendix II of this part.(3) Start the diurnal emission test after the engine is stabilized at room temperatures, but within 36 hours after the engine operation specified in paragraph (e)(2) of this section.(4) You may not separately measure permeation emissions from nonmetal fuel tanks for subtracting from the diurnal emission measurement.(5) Note that you may omit testing for evaporative emissions during certification if you certify by design, as specified in § 1048.245 .(f) You may use special or alternate procedures to the extent we allow them under 40 CFR 1065.10 .(g) This subpart is addressed to you as a manufacturer, but it applies equally to anyone who does testing for you, and to us when we perform testing to determine if your engines meet emission standards. 70 FR 40476 , July 13, 2005, as amended at 73 FR 59239 , Oct. 8, 2008; 74 FR 56510 , Oct. 30, 2009; 86 FR 34515 , June 29, 2021; 88 FR 4665 , Jan. 24, 2023 86 FR 34515 , 7/29/2021; 88 FR 4665 , 3/27/2023