---
kind: "section"
citation: "49 C.F.R. § 537.9"
title: "49"
number: "537.9"
heading: "Determination of fuel economy values and average fuel economy."
url: "https://uscodex.org/cfr/49/537.9"
---

# §537.9. Determination of fuel economy values and average fuel economy.

- (a) **Vehicle subconfiguration fuel economy values.**
  - (1) For each vehicle subconfiguration for which a fuel economy value is required under [paragraph (c)](#c) of this section and has been determined and approved under [40 CFR part 600](/cfr/40/part600.md), the manufacturer shall submit that fuel economy value.
  - (2) For each vehicle subconfiguration specified in [paragraph (a)(1)](#a-1) of this section for which a fuel economy value approved under [40 CFR part 600](/cfr/40/part600.md), does not exist, but for which a fuel economy value determined under [40 CFR part 600](/cfr/40/part600.md) exists, the manufacturer shall submit that fuel economy value.
  - (3) For each vehicle subconfiguration specified in [paragraph (a)(1)](#a-1) of this section for which a fuel economy value has been neither determined nor approved under [40 CFR part 600](/cfr/40/part600.md), the manufacturer shall submit a fuel economy value based on tests or analyses comparable to those prescribed or permitted under [40 CFR part 600](/cfr/40/part600.md) and a description of the test procedures or analytical methods used.
  - (4) For each vehicle configuration for which a fuel economy value is required under [paragraph (c)](#c) of this section and has been determined and approved under [40 CFR part 600](/cfr/40/part600.md), the manufacturer shall submit that fuel economy value.
- (b) **Base level and model type fuel economy values.** For each base level and model type, the manufacturer shall submit a fuel economy value based on the values submitted under [paragraph (a)](#a) of this section and calculated in the same manner as base level and model type fuel economy values are calculated for use under [subpart F](/cfr/49/subpartF.md) of [40 CFR part 600](/cfr/40/part600.md).
- (c) **Average fuel economy.** Average fuel economy must be based upon fuel economy values calculated under [paragraph (b)](#b) of this section for each model type and must be calculated in accordance with [subpart F](/cfr/49/subpartF.md) of [40 CFR part 600](/cfr/40/part600.md), except that fuel economy values for running changes and for new base levels are required only for those changes made or base levels added before the average fuel economy is required to be submitted under this part.

## Notes

### Authority

Authority: 49 U.S.C. 32907; delegation of authority at 49 CFR 1.95.

### Source

Source: 87 FR 26087, May 2, 2022, unless otherwise noted.