§ 86.1823-08 — Durability demonstration procedures for exhaust emissions.
This text of 40 C.F.R. § 86.1823-08 (Durability demonstration procedures for exhaust emissions.) is published on Counsel Stack Legal Research, covering United States primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.
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§ 86.1823-08 Durability demonstration procedures for exhaust emissions. Link to an amendment published at 91 FR 7762, Feb. 18, 2026. This section describes durability demonstration procedures for exhaust emissions. Eligible small-volume manufacturers or small-volume test groups may optionally meet the requirements of §§ 86.1826 and 86.1838 instead of the requirements of paragraphs (a) through (m) of this section. A separate durability demonstration is required for each durability group.
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This section describes durability demonstration procedures for exhaust emissions. Eligible small-volume manufacturers or small-volume test groups may optionally meet the requirements of §§ 86.1826 and 86.1838 instead of the requirements of paragraphs (a) through (m) of this section. A separate durability demonstration is required for each durability group.
(a) Durability program objective. The durability program must predict an expected in-use emission deterioration rate and emission level that effectively represents a significant majority of the distribution of emission levels and deterioration in actual use over the full and intermediate useful life of candidate in-use vehicles of each vehicle design which uses the durability program.
(b) Required durability demonstration. Manufacturers must conduct a durability demonstration for each durability group using a procedure specified in either paragraph (c), (d), or (e) of this section.
(c) Standard whole-vehicle durability procedure. This procedure consists of conducting mileage accumulation and periodic testing on the durability data vehicle, selected under the provisions of § 86.1822 described as follows:
(1) Mileage accumulation must be conducted using the standard road cycle (SRC). The SRC is described in appendix V of this part.
(i) Mileage accumulation on the SRC may be conducted on a track or on a chassis mileage accumulation dynamometer. Alternatively, the entire engine and emission control system may be aged on an engine dynamometer using methods that will replicate the aging that occurs on the road for that vehicle following the SRC.
(ii) The fuel used for mileage accumulation must comply with the mileage accumulation fuel provisions of § 86.113 for the applicable fuel type (e.g., gasoline or diesel fuel).
(iii) The DDV must be ballasted to a minimum of the loaded vehicle weight for light-duty vehicles and light light-duty trucks and a minimum of the ALVW for all other vehicles.
(iv) The mileage accumulation dynamometer must be setup as follows:
(A) The simulated test weight will be the equivalent test weight specified in § 86.129 using a weight basis of the loaded vehicle weight for light-duty vehicles and light light-duty trucks, and ALVW for all other vehicles.
(B) The road force simulation will be determined according to the provisions of § 86.129.
(C) The manufacturer will control the vehicle, engine, and/or dynamometer as appropriate to follow the SRC using good engineering judgement.
(2) Mileage accumulation must be conducted for at least 75% of the applicable full useful life mileage period specified in § 86.1805. If the mileage accumulation is less than 100% of the full useful life mileage, then the DF calculated according to the procedures of paragraph (f)(1)(ii) of this section must be based upon a line projected to the full-useful life mileage using the upper 80 percent statistical confidence limit calculated from the emission data.
(3) If a manufacturer elects to calculate a DF pursuant to paragraph (f)(1) of this section, then it must conduct at least one FTP emission test at each of five different mileage points selected using good engineering judgement. Additional testing may be conducted by the manufacturer using good engineering judgement. The required testing must include testing at 5,000 miles and at the highest mileage point run during mileage accumulation (e.g. the full useful life mileage). Different testing plans may be used providing that the manufacturer determines, using good engineering judgement, that the alternative plan would result in an equivalent or superior level of confidence in the accuracy of the DF calculation compared to the testing plan specified in this paragraph.
(d) Standard bench-aging durability procedure. This procedure is not applicable to diesel fueled vehicles or vehicles which do not use a catalyst as the principle after-treatment emission control device. This procedure requires installation of the catalyst-plus-oxygen-sensor system on a catalyst aging bench. Aging on the bench is conducted by following the standard bench cycle (SBC) for the period of time calculated from the bench aging time (BAT) equation. The BAT equation requires, as input, catalyst time-at-temperature data measured on the SRC.
(1) Standard bench cycle (SBC). Standard catalyst bench aging is conducted following the SBC
(i) The SBC must be run for the period of time calculated from the BAT equation.
(ii) The SBC is described in appendix VII to part 86.
(2) Catalyst time-at-temperature data (i) Catalyst temperature must be measured during at least two full cycles of the SRC.
(ii) Catalyst temperature must be measured at the highest temperature location in the hottest catalyst on the DDV. Alternatively, the temperature may be measured at another location providing that it is adjusted to represent the temperature measured at the hottest location using good engineering judgement.
(iii) Catalyst temperature must be measured at a minimum rate of one hertz (one measurement per second).
(iv) The measured catalyst temperature results must be tabulated into a histogram with temperature bins of no larger than 25 °C.
(3) Bench-aging time. Bench aging time is calculated using the bench aging time (BAT) equation as follows:
te for a temperature bin = th e((R/Tr)−(R/Tv))
(4) Effective reference temperature on the SBC. The effective reference temperature of the standard bench cycle (SBC) is determined for the actual catalyst system design and actual aging bench which will be used using the following procedures:
(i) Measure time-at-temperature data in the catalyst system on the catalyst aging bench following the SBC.
(A) Catalyst temperature must be measured at the highest temperature location of the hottest catalyst in the system. Alternatively, the temperature may be measured at another location providing that it is adjusted to represent the temperature measured at the hottest location using good engineering judgement.
(B) Catalyst temperature must be measured at a minimum rate of one hertz (one measurement per second) during at least 20 minutes of bench aging.
(C) The measured catalyst temperature results must be tabulated into a histogram with temperature bins of no larger than 10 °C.
(ii) The BAT equation must be used to calculate the effective reference temperature by iterative changes to the reference temperature (Tr) until the calculated aging time equals the actual time represented in the catalyst temperature histogram. The resulting temperature is the effective reference temperature on the SBC for that catalyst system and aging bench.
(5) Catalyst Aging Bench. The manufacturer must design, using good engineering judgement, a catalyst aging bench that follows the SBC and delivers the appropriate exhaust flow, exhaust constituents, and exhaust temperature to the face of the catalyst.
(i) A manufacturer may use the criteria and equipment discussed in appendix VIII to part 86 to develop its catalyst aging bench without prior Agency approval. The manufacturer may use another design that results in equivalent or superior results with advance Agency approval.
(ii) All bench aging equipment and procedures must record appropriate information (such as measured A/F ratios and time-at-temperature in the catalyst) to assure that sufficient aging has actually occurred.
(6) Required Testing. If a manufacturer is electing to calculate a DF (as discussed in paragraph (f)(1) of this section), then it must conduct at least two FTP emissions tests on the DDV before bench aging of emission control hardware and at least two FTP emission tests on the DDV after the bench-aged emission hardware is re-installed. Additional testing may be conducted by the manufacturer using good engineering judgement.
(e) Additional durability procedures—(1) Whole vehicle durability procedures. A manufacturer may use either a customized SRC or an alternative road cycle for the required durability demonstration, with prior EPA approval.
(i) Customized SRC. A customized SRC is the SRC run for a different number of miles and/or using a different mileage accumulation fuel with higher levels of certain compounds that may lead to catalyst poisoning, such as phosphorus, sulfur and lead, than specified in paragraph (c)(1)(ii) of this section.
(ii) Alternative road cycle. An alternative cycle is a whole vehicle mileage accumulation cycle that uses a different speed-versus-time trace than the SRC, conducted for either the full useful life mileage or for less than full useful life mileage. An alternative road cycle may also include the use of fuel with higher levels of certain compounds that may lead to catalyst poisoning, such as phosphorus, sulfur and lead, than specified in paragraph (c)(1)(ii) of this section.
(iii) Approval criteria. The manufacturer must obtain approval from EPA prior to using a customized/alternative road cycle. EPA may approve a customized/alternative cycle when the manufacturer demonstrates that the cycle is expected to achieve the durability program objective of paragraph (a) of this section for the breadth of vehicles using the customized/alternative cycle. To obtain approval the manufacturer must submit all the following information and perform all the following analyses:
(A) The manufacturer must supply in-use FTP emission data on past model year vehicles which are applicable to the vehicle designs it intends to cover with the customized/alternative cycle.
(1) The amount of in-use emission data required to demonstrate the effectiveness of a customized/alternative cycle in meeting the durability objective is based on whether the customized/alternative cycle is more or less severe than the SRC. In most cases, EPA will accept a minimum of 20 candidate in-use vehicles tested as-received on the FTP cycle. If the customized/alternative cycle is significantly more severe than the SRC, EPA may accept less data. Conversely, if the customized/alternative cycle is significantly less severe than the SRC, EPA may require more data, up to a maximum of 30 vehicles.
(2) This data set must consist of randomly procured vehicles from actual customer use. The vehicles selected for procurement must cover the breadth of the vehicles that the manufacturer intends to certify using the customized/alternative cycle. Vehicles should be procured and FTP tested in as-received condition under the guidelines of the high mileage IUVP program (ref: 40 CFR 86.1845-04).
(3) Manufacturers may use previously generated in-use data from the CAP 2000 IUVP or the RDP “reality check” in-use program as well as other sources of in-use emissions data for approval under this section.
(4) Manufacturers must remove unrepresentative data from the data set using good engineering judgement. The manufacturer must provide EPA with the data removed from the analysis and a justification for the removal of that data.
(5) Manufacturers may supply additional in-use data.
(B) The manufacturer must submit an analysis which includes a comparison of the relative stringency of the customized/alternative cycle to the SRC and a calculated equivalency factor for the cycle.
(1) The equivalency factor may be determined by an evaluation of the SRC and the customized/alternative cycle using catalyst time-at-temperature data from both cycles with the BAT equation to calculate the required bench aging time of each cycle. Once the bench aging time is calculated for each cycle, the equivalency factor is the ratio described by dividing the bench aging time on the customized/alternative cycle by the bench aging time on the SRC.
(2) If emissions data is available from the SRC, as well as time-at-temperature data, then that emissions information may be included in the evaluation of the relative stringency of the two cycles and the development of the equivalency factor.
(3) A separate equivalency factor may be determined for each test group, or test groups may be combined together (using good engineering judgement) to calculate a single equivalency factor.
(C) The manufacturer must submit an analysis which evaluates whether the durability objective will be achieved for the vehicle designs which will be certified using the customized/alternative cycle. The analysis must address of the following elements:
(1) How the durability objective has been achieved using the data submitted in paragraph (e)(1)(iii)(A) of this section.
(2) How the durability objective will be achieved for the vehicle designs which will be covered by the customized/alternative cycle. This analysis should consider the emissions deterioration impact of the design differences between the vehicles included in the data set required in (e)(1)(iii)(A) of this section and the vehicle designs that the manufacturer intends to certify using the customized/alternative cycle.
(2) Bench-aging durability procedures. A manufacturer may use a customized or alternative bench aging durability procedure for a required durability demonstration, if approved as described in paragraphs (e)(2)(i) through (vii) of this section. A customized/alternative bench aging procedure must use vehicle performance data (such as catalyst temperature) measured on an approved road cycle as part of the algorithm to calculate bench aging time. The manufacturer must obtain approval from the Agency prior to using a customized bench durability procedure.
(i) The lower control temperature on the SBC may be modified without prior EPA approval provided that the high control temperature is set 90 °C above the lower control temperature and an approved BAT equation is used to calculate bench aging time.
(ii) The R-factor used in EPA's BAT equation may be determined experimentally using EPA's standard procedures (specified in appendix IX of this part) without prior EPA approval. Other experimental techniques to calculate the R-factor require advance EPA approval. To obtain approval, the manufacturer must demonstrate that the calculated bench aging time results in the same (or larger) amount of emission deterioration as the associated road cycle.
(iii) The A-factor used in EPA's BAT equation may be modified, using good engineering judgement without prior EPA approval, to ensure that the modified durability process will achieve the durability objective of paragraph (a) of this section.
(iv) Bench aging may be conducted using fuel with additional compounds that may lead to catalyst poisoning, such as phosphorus, sulfur or lead, without prior EPA approval. A manufacturer using fuel with these additional compounds may either calculate a new R-factor or A-factor to assure that the durability objective of paragraph (a) of this section is properly achieved regardless of the use of worst-case fuel, in which case the approval criteria for those changes would apply.
(v) An approved customized/alternative road cycle may be used to develop catalyst temperature histograms for use in the BAT equation without additional EPA approval beyond the original approval necessary to use that cycle for mileage accumulation.
(vi) A different bench cycle than the SBC may be used during bench aging with prior EPA approval. To obtain approval the manufacturer must demonstrate that bench aging for the appropriate time on the new bench cycle provides the same or larger amount of emission deterioration as the associated road cycle.
(vii) A different method to calculate bench aging time may be used with prior EPA approval. To obtain approval the manufacturer must demonstrate that bench aging for the time calculated by the alternative method results in the same or larger amount of emission deterioration as the associated road cycle.
(f) Use of deterioration program to determine compliance with the standard. A manufacturer may select from two methods for using the results of the deterioration program to determine compliance with the applicable emission standards. Either a deterioration factor (DF) is calculated and applied to the emission data vehicle (EDV) emission results or aged components are installed on the EDV prior to emission testing.
(1) Deterioration factors. (i) Deterioration factors are calculated using all FTP emission test data generated during the durability testing program except as noted:
(A) Multiple tests at a given mileage point are averaged together unless the same number of tests are conducted at each mileage point.
(B) Before and after maintenance test results are averaged together.
(C) Zero-mile test results are excluded from the calculation.
(D) Total hydrocarbon (THC) test points beyond the 50,000-mile (useful life) test point are excluded from the intermediate useful life deterioration factor calculation.
(E) A procedure may be employed to identify and remove from the DF calculation those test results determined to be statistical outliers providing that the outlier procedure is consistently applied to all vehicles and data points and is approved in advance by the Administrator.
(ii) The deterioration factor must be based on a linear regression, or another regression technique approved in advance by the Administrator. The deterioration must be a multiplicative or additive factor. Separate factors will be calculated for each regulated emission constituent and for the full and intermediate useful life periods as applicable. Separate DF's are calculated for each durability group except as provided in § 86.1839.
(A) A multiplicative DF will be calculated by taking the ratio of the full or intermediate useful life mileage level, as appropriate (rounded to four decimal places), divided by the stabilized mileage (reference § 86.1831-01(c), e.g., 4000-mile) level (rounded to four decimal places) from the regression analysis. The result must be rounded to three-decimal places of accuracy. The rounding required in this paragraph must be conducted in accordance with § 86.1837. Calculated DF values of less than one must be changed to one for the purposes of this paragraph.
(B) An additive DF will be calculated to be the difference between the full or intermediate useful life mileage level (as appropriate) minus the stabilized mileage (reference § 86.1831-01(c), e.g., 4000-mile) level from the regression analysis. The full useful life regressed emission value, the stabilized mileage regressed emission value, and the DF result must be rounded to the same precision and using the same procedures as the raw emission results according to the provisions of § 86.1837-01. Calculated DF values of less than zero must be changed to zero for the purposes of this paragraph.
(iii) For Tier 3 vehicles, the DF calculated by these procedures will be used for determining full and intermediate useful life compliance with FTP exhaust emission standards, SFTP exhaust emission standards, and cold CO emission standards. At the manufacturer's option and using procedures approved by the Administrator, a separate DF may be calculated exclusively using cold CO test data to determine compliance with cold CO emission standards. Also, at the manufacturer's option and using procedures approved by the Administrator, a separate DF may be calculated exclusively using US06 and/or air conditioning (SC03) test data to determine compliance with the SFTP emission standards.
(iv) For Tier 4 vehicles, the DF calculated by these procedures may be used for determining compliance with all the standards identified in § 86.1811-27. At the manufacturer's option and using procedures approved by the Administrator, manufacturers may calculate a separate DF for the following standards and driving schedules:
(A) Testing to determine compliance with cold temperature emission standards.
(B) US06 testing.
(C) SC03 testing.
(D) HFET.
(E) Mid-temperature intermediate soak testing.
(F) Early driveaway testing.
(G) High-power PHEV engine starts.
(2) Installation of aged components on emission data vehicles. For full and intermediate useful life compliance determination, the manufacturer may elect to install aged components on an EDV prior to emission testing rather than applying a deterioration factor. Different sets of components may be aged for full and intermediate useful life periods. Components must be aged using an approved durability procedure that complies with paragraph (b) of this section. The list of components to be aged and subsequently installed on the EDV must selected using good engineering judgment.
(g) [Reserved]
(h) Application of the durability procedure to future durability groups. The manufacturer may apply a durability procedure approved under paragraphs (c), (d) or (e) of this section to a durability group, including durability groups in future model years, if the durability process will achieve the objective of paragraph (a) of this section for that durability group. The manufacturer must use good engineering judgment in determining the applicability of an approved durability procedure to a durability group.
(1) Modifications to a durability procedure. (i) Standard durability procedures. The manufacturer may modify a standard durability procedure (allowed in paragraphs (c) or (d) of this section) by increasing or decreasing the number of miles run on the SRC to represent full or intermediate useful life emissions deterioration or by changing the A-Factor in the BAT equation for a bench aging, using good engineering judgment, to ensure that the modified procedure will achieve the objective of paragraph (a) of this section for that durability group.
(ii) Customized/Alternative durability procedures. The manufacturer may modify an alternative/customized durability procedure approved under the provisions of paragraph (e) of this section, using good engineering judgment, for the purposes of ensuring that the modified procedure will achieve the objective of paragraph (a) of this section for that durability group.
(2) The manufacturer must notify the Administrator of its determination to use an approved (or modified) durability procedure on particular test groups and durability groups prior to, or concurrently with, its submission of the Application for Certification for the affected test groups (notification at an annual preview meeting scheduled before the manufacturer begins certification activities for the model year is preferred).
(3) Prior to certification, the Administrator may reject the manufacturer's determination in paragraph (h) of this section to apply an approved or modified durability procedure for a durability group or test group if:
(i) It is not made using good engineering judgment,
(ii) It fails to properly consider data collected under the provisions of §§ 86.1845-04, 86.1846-01, and 86.1847-01 or other information, or
(iii) The Administrator determines that the durability procedure has not been shown to achieve the objective of paragraph (a) of this section for particular test groups which the manufacturer plans to cover with the durability procedure.
(i) Evaluation of the certification durability procedures based on in-use emissions data. (1) Manufacturers must use the information gathered from the IUVP, as well as other sources of in-use emissions data, to periodically review whether the durability procedure it employs achieves the objective specified in paragraph (a) of this section.
(2) Required analysis of a manufacturer's approved durability procedures. (i) In addition to any periodic reviews under paragraph (i)(1) of this section, a manufacturer must conduct a review of whether the durability procedure it employs achieves the durability objective specified in paragraph (a) of this section when the criteria for additional testing specified in § 86.1846 (b) are activated.
(ii) These criteria are evaluated independently for all applicable FTP emission constituents.
(iii) This analysis must be performed for each test group certified by the manufacturer.
(iv) These procedures apply to the EPA standard durability procedures discussed in paragraphs (c) and (d) of this section as well as durability procedures approved under paragraph (e) of this section, including modifications under paragraph (h) of this section.
(v) The analysis must be submitted to EPA no later than 60 days after the submission of the IUVP data report specified in § 86.1847(f).
(3) EPA may require a manufacturer to perform an analysis as described in paragraph (i)(2) of this section if EPA is concerned that the manufacturer's durability procedure may not achieve the durability objective of paragraph (a) of this section.
(j) If, based on the analysis required in paragraph (i) of this section and/or any other information, EPA determines that the durability procedure does not achieve the durability objective of paragraph (a) of this section, EPA may withdraw approval to use the durability procedure or condition approval on modifications to the durability procedure. Such withdrawal or conditional approval will apply to future applications for certification and to the portion of the manufacturer's product line (or the entire product line) that the Administrator determines to be affected. Prior to such a withdrawal the Administrator will give the manufacturer a preliminary notice at least 60 days prior to the final decision. During this period, the manufacturer may submit technical discussion, statistical analyses, additional data, or other information which is relevant to the decision. The Administrator will consider all information submitted by the deadline before reaching a final decision.
(k) If EPA withdraws approval, under the provisions of paragraph (j) of this section, for a durability procedure approved under the provisions of paragraphs (c) and/or (d) of this section, the following procedures apply:
(1) The manufacturer must select one of the following options for future applications for certification for the applicable portion of the manufacturers product-line affect by the Agency's decision:
(i) Increase future DFs calculated using the applicable durability process by the average percent-difference between certification levels and IUVP data; or
(ii) Increase the miles driven on the SRC or the aging time calculated by the BAT equation by the average percent-difference between certification levels and IUVP data, or
(iii) The manufacturer may obtain approval for a new customized durability process, as allowed in paragraph (e) of this section, that has been demonstrated to meet the durability objective.
(2) If EPA's decision to withdraw approval under the provisions of paragraph (j) of this section is based on fewer than 20 tests, the Administrator may require a smaller adjustment than specified in paragraph (k)(1)(i) or (ii) of this section.
(l) Any manufacturer may request a hearing on the Administrator's withdrawal of approval in paragraphs (j) or (k) of this section. The request must be in writing and must include a statement specifying the manufacturer's objections to the Administrator's determinations, and data in support of such objection. If, after review of the request and supporting data, the Administrator finds that the request raises a substantial factual issue, she/he must provide the manufacturer a hearing in accordance with § 86.1853-01 with respect to such issue.
(m) Durability demonstration procedures for vehicles subject to the greenhouse gas exhaust emission standards specified in § 86.1818. Determine a deterioration factor for each exhaust constituent as described in this paragraph (m) and in 40 CFR 600.113-12(h) through (m) to calculate the composite CREE DF value. (1) CO2. (i) Unless otherwise specified under paragraph (m)(1)(ii) or (iii) of this section, manufacturers may use a multiplicative CO2 deterioration factor of one or an additive deterioration factor of zero to determine full useful life emissions for the FTP and HFET tests.
(ii) Based on an analysis of industry-wide data, EPA may periodically establish and/or update the deterioration factor for CO2 emissions, including air conditioning and other credit-related emissions. Deterioration factors established and/or updated under this paragraph (m)(1)(ii) will provide adequate lead time for manufacturers to plan for the change.
(iii) For plug-in hybrid electric vehicles and any other vehicle model the manufacturer determines will experience increased CO2 emissions over the vehicle's useful life, consistent with good engineering judgment, manufacturers must either install aged batteries and other relevant components on test vehicles as provided in paragraph (f)(2) of this section, determine a deterioration factor based on testing, or provide an engineering analysis that the vehicle is designed such that CO2 emissions will not increase over the vehicle's useful life. Manufacturers may test using the whole-vehicle mileage accumulation procedures in § 86.1823-08 (c) or (d)(1), or manufacturers may request prior EPA approval for an alternative durability procedure based on good engineering judgment. For the testing option, each FTP test performed on the durability data vehicle selected under § 86.1822 must also be accompanied by an HFET test, and combined FTP/HFET CO2 results determined by averaging the city (FTP) and highway (HFET) CO2 values, weighted 0.55 and 0.45 respectively. The deterioration factor will be determined for this combined CO2 value. Calculated multiplicative deterioration factors that are less than one shall be set to equal one, and calculated additive deterioration factors that are less than zero shall be set to zero.
(2) N2O and CH4. (i) For manufacturers complying with the FTP emission standards for N2O and CH4 specified in § 86.1818-12(f)(1) or determined under § 86.1818-12(f)(3), FTP-based deterioration factors for N2O and CH4 shall be determined according to the provisions of paragraphs (a) through (l) of this section.
(ii) For manufacturers complying with the fleet averaging option for N2O and CH4 as allowed under § 86.1818-12(f)(2), deterioration factors based on FTP testing shall be determined and may be used to determine full useful life emissions for the FTP and HFET tests. The manufacturer may at its option determine separate deterioration factors for the FTP and HFET test cycles, in which case each FTP test performed on the durability data vehicle selected under § 86.1822 of this part must also be accompanied by an HFET test.
(iii) For the 2012 through 2016 model years only, manufacturers may use alternative deterioration factors. For N2O, the alternative deterioration factor to be used to adjust FTP and HFET emissions is the deterioration factor determined for (or derived from, using good engineering judgment) NOX emissions according to the provisions of this section. For CH4, the alternative deterioration factor to be used to adjust FTP and HFET emissions is the deterioration factor determined for (or derived from, using good engineering judgment) NMOG or NMHC emissions according to the provisions of this section.
(3) Other carbon-related exhaust emissions. FTP-based deterioration factors shall be determined for carbon-related exhaust emissions (CREE), hydrocarbons, and CO according to the provisions of paragraphs (a) through (l) of this section. The FTP-based deterioration factor shall be used to determine full useful life emissions for both the FTP (city) and HFET (highway) test cycles. The manufacturer may at its option determine separate deterioration factors for the FTP and HFET test cycles, in which case each FTP test performed on the durability data vehicle selected under § 86.1822 must also be accompanied by an HFET test. In lieu of determining emission-specific deterioration factors for the specific hydrocarbons of CH3OH (methanol), HCHO (formaldehyde), C2H5OH (ethanol), and C2H4O (acetaldehyde) as may be required for some alternative fuel vehicles, manufacturers may use the additive or multiplicative deterioration factor determined for (or derived from, using good engineering judgment) NMOG or NMHC emissions according to the provisions of this section.
(4) Air Conditioning leakage and efficiency or other emission credit requirements to comply with exhaust CO2 standards. Manufactures will attest to the durability of components and systems used to meet the CO2 standards. Manufacturers may submit engineering data to provide durability demonstration. Deterioration factors do not apply to emission-related components and systems used to generate air conditioning leakage and/or efficiency credits.
(n) Emission component durability. The manufacturer shall use good engineering judgment to determine that all emission-related components are designed to operate properly for the full useful life of the vehicles in actual use.
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40 C.F.R. § 86.1823-08, Counsel Stack Legal Research, https://law.counselstack.com/cfr/40/86/86.1823-08.