(a) Applicability. The provisions of this subpart apply for certain types of new heavy-duty engines and vehicles as described in this section. As described in paragraph (j) of this section, most of this subpart no longer applies starting with model year 2027. Note that this subpart does not apply for light-duty vehicles, light-duty trucks, medium-duty passenger vehicles, or vehicles at or below 14,000 pounds GVWR that have no propulsion engine, such as electric vehicles; see subpart S of this part for requirements that apply for those vehicles. In some cases, manufacturers of heavy-duty engines and vehicles can choose to meet the requirements of this subpart or the requirements of subpart S of this part; those provisions are therefore considered optional, but only to the extent that manufacturers comply with the other set of requirements. In cases where a provision applies only for a certain vehicle group based on its model year, vehicle class, motor fuel, engine type, or other distinguishing characteristics, the limited applicability is cited in the appropriate section. The provisions of this subpart apply for certain heavy-duty engines and vehicles as follows:

(1) The provisions of this subpart related to exhaust emission standards apply for diesel-cycle and Otto-cycle heavy-duty engines installed in vehicles above 14,000 pounds GVWR; however, these vehicles may instead be certified under subpart S of this part in certain circumstances as specified in § 86.1801.

(2) The provisions of this subpart related to exhaust emission standards apply for engines that will be installed in incomplete heavy-duty vehicles at or below 14,000 pounds GVWR; however, these vehicles may instead be certified under subpart S of this part as specified in § 86.1801.

(3) Diesel-cycle and Otto-cycle complete heavy-duty vehicles at or below 14,000 pounds GVWR and the corresponding engines are not subject to the provisions of this subpart related to exhaust emission standards, except that these provisions are optional for diesel-cycle engines installed in such vehicles until those vehicles become subject to the Tier 3 standards under § 86.1816-18.

(4) The provisions of this subpart related to evaporative emission standards apply for diesel-cycle and Otto-cycle heavy-duty vehicles as follows:

(i) These provisions do not apply for vehicles at or below 14,000 pounds GVWR.

(ii) Vehicles above 14,000 pounds GVWR must meet evaporative emission standards as specified in 40 CFR 1037.103. This involves meeting the standards specified in §§ 86.008-10(b) and 86.007-11(b)(3) and (4) until the Tier 3 standards in § 86.1813 start to apply.

(iii) Note that diesel-fueled vehicles are not subject to evaporative emissions under this part.

(5) The provisions of this subpart related to onboard diagnostics apply for diesel-cycle and Otto-cycle heavy-duty engines and vehicles as follows:

(i) Engines installed in vehicles above 14,000 pounds GVWR must meet the onboard diagnostic requirements specified in § 86.010-18.

(ii) Engines installed in vehicles at or below 14,000 pounds GVWR must meet the onboard diagnostic requirements specified in § 86.1806.

(b) Relationship to subpart S of this part. Unless specified otherwise, if engines are not subject to provisions of this subpart or if manufacturers choose not to meet optional provisions of this subpart as described in paragraph (a) of this section, those engines must be installed in vehicles meeting the corresponding requirements under subpart S of this part. If a vehicle and its installed engine comply with a mix of provisions from this subpart and from subpart S of this part, the vehicle must be certified under subpart S of this part, and the engine does not need to be certified separately.

(c) Greenhouse gas emission standards. See 40 CFR parts 1036 and 1037 for greenhouse gas emission standards that apply for heavy-duty engines and vehicles.

(d) Non-petroleum fueled vehicles. Standards and requirements apply to model year 2016 and later non-petroleum fueled motor vehicles as follows:

(1) The standards and requirements of this part apply as specified for vehicles fueled with methanol, natural gas, and LPG.

(2) The standards and requirements of subpart S of this part apply as specified for light-duty vehicles and light-duty trucks.

(3) The standards and requirements of this part applicable to methanol-fueled heavy-duty vehicles and engines (including flexible fuel vehicles and engines) apply to heavy-duty vehicles and engines fueled with any oxygenated fuel (including flexible fuel vehicles and engines). Most significantly, this means that the hydrocarbon standards apply as NMHCE and the vehicles and engines must be tested using the applicable oxygenated fuel according to the test procedures in 40 CFR part 1065 applicable for oxygenated fuels. For purposes of this paragraph (d), oxygenated fuel means any fuel containing at least 50 volume percent oxygenated compounds. For example, a fuel mixture of 85 gallons of ethanol and 15 gallons of gasoline is an oxygenated fuel, while a fuel mixture of 15 gallons of ethanol and 85 gallons of gasoline is not an oxygenated fuel.

(4) The standards and requirements of 40 CFR part 1037 apply for vehicles above 14,000 pounds GVWR that have no propulsion engine, such as electric vehicles. Electric heavy-duty vehicles may not generate PM emission credits. Electric heavy-duty vehicles may not generate NOX emission credits except as allowed under 40 CFR part 1037.

(5) The standards and requirements of this part applicable to diesel-fueled heavy-duty vehicles and engines apply to all other heavy-duty vehicles and engines not otherwise addressed in this paragraph (d).

(6) See 40 CFR parts 1036 and 1037 for requirements related to greenhouse gas emissions.

(7) Manufacturers may voluntarily certify to the standards of paragraphs (d)(3) through (5) of this section before model year 2016. Note that other provisions in this part require compliance with the standards described in paragraphs (d)(1) and (2) of this section for model years before 2016.

(e) Small volume manufacturers. Special certification procedures are available for any manufacturer whose projected combined U.S. sales of light-duty vehicles, light-duty trucks, heavy-duty vehicles, and heavy-duty engines in its product line (including all vehicles and engines imported under the provisions of 40 CFR 85.1505 and 85.1509) are fewer than 10,000 units for the model year in which the manufacturer seeks certification. To certify its product line under these optional procedures, the small-volume manufacturer must first obtain the Administrator's approval. The manufacturer must meet the eligibility criteria specified in § 86.098-14(b) before the Administrator's approval will be granted. The small-volume manufacturer's certification procedures are described in § 86.098-14.

(f) Optional procedures for determining exhaust opacity. (1) The provisions of subpart I of this part apply to tests which are performed by the Administrator, and optionally, by the manufacturer.

(2) Measurement procedures, other than those described in subpart I of this part, may be used by the manufacturer provided the manufacturer satisfies the requirements of § 86.007-23(f).

(3) When a manufacturer chooses to use an alternative measurement procedure, it has the responsibility to determine whether the results obtained by the procedure will correlate with the results which would be obtained from the measurement procedure in subpart I of this part. Consequently, the Administrator will not routinely approve or disapprove any alternative opacity measurement procedure or any associated correlation data which the manufacturer elects to use to satisfy the data requirements for subpart I of this part.

(4) If a confirmatory test is performed and the results indicate there is a systematic problem suggesting that the data generated under an optional alternative measurement procedure do not adequately correlate with data obtained in accordance with the procedures described in subpart I of this part, EPA may require that all certificates of conformity not already issued be based on data obtained from procedures described in subpart I of this part.

(g) Clean alternative fuel conversions. The provisions of this subpart also apply for clean alternative fuel conversions as defined in 40 CFR 85.502 of all vehicles described in paragraph (a) of this section.

(h) Turbine engines. Turbine engines are deemed to be compression-ignition engines for purposes of this part.

(i) [Reserved]

(j) Transition to 40 CFR parts 1036 and 1037. Except for § 86.010-38(j), this subpart no longer applies starting with model year 2027. Individual provisions in 40 CFR parts 1036 and 1037 apply instead of the provisions of this subpart before model year 2027 as specified in this subpart and 40 CFR parts 1036 and 1037.