---
kind: "section"
citation: "40 C.F.R. § 1048.501"
title: "40"
number: "1048.501"
heading: "How do I run a valid emission test?"
url: "https://uscodex.org/cfr/40/1048.501"
---

# §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](/cfr/40/part1065.md) to determine whether engines meet the duty-cycle emission standards in § [1048.101(a)](/cfr/40/1048.101.md?p=a) and [(b)](/cfr/40/1048.101.md?p=b). Measure the emissions of all the pollutants we regulate in [§ 1048.101](/cfr/40/1048.101.md) using the sampling procedures specified in [40 CFR part 1065](/cfr/40/part1065.md). Measure CO2, N2O, and CH4 as described in [§ 1048.235](/cfr/40/1048.235.md). Use the applicable duty cycles specified in §§ [1048.505](/cfr/40/1048.505.md) and [1048.510](/cfr/40/1048.510.md).
- (b) [Section 1048.515](/cfr/40/1048.515.md) describes the supplemental procedures for evaluating whether engines meet the field-testing emission standards in [§ 1048.101(c)](/cfr/40/1048.101.md?p=c).
- (c) Use the fuels and lubricants specified in [40 CFR part 1065](/cfr/40/part1065.md), [subpart H](/cfr/40/subpartH.md), to perform valid tests for all the testing we require in this part, except as noted in [§ 1048.515](/cfr/40/1048.515.md).
  - (1) Use gasoline meeting the specifications described in [40 CFR 1065.710(c)](/cfr/40/1065.710.md?p=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)](/cfr/40/1065.710.md?p=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](/cfr/40/1065.405.md), 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](/cfr/40/1060.525.md), subject to the following provisions:
  - (1) Precondition nonmetal fuel tanks as specified in 40 CFR [1060.520(a)](/cfr/40/1060.520.md?p=a) and [(b)](/cfr/40/1060.520.md?p=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)](/cfr/40/86.132-96.md?p=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)](#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](/cfr/40/1048.245.md).
- (f) You may use special or alternate procedures to the extent we allow them under [40 CFR 1065.10](/cfr/40/1065.10.md).
- (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.

## Notes

### Amendments

[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]

### Authority

Authority: 42 U.S.C. 7401-7671q.

### Source

Source: 67 FR 68347, Nov. 8, 2002, unless otherwise noted.

### Amendments

[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]