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Why a Diesel Nozzle Won't Fit a Gas Car

Cover of the Short: Why a Diesel Nozzle Won't Fit a Gas Car▶ Watch the Short

The answer

It's on purpose: since the 1970s unleaded switch, US law caps gasoline nozzles at 0.84 in and gas cars got a hole that small. Diesel nozzles are bigger. The catch: a gas nozzle fits a diesel car fine.

Sources (3)

  1. Original rule: 40 CFR 80.22(f) — gasoline nozzle terminal end outside diameter "not be greater than 0.840 inches (2.134 centimeters)" (eCFR point-in-time, 2021-06-01). It came with the 1970s unleaded-gasoline rules. https://www.ecfr.gov/on/2021-06-01/title-40/section-80.22
  2. Still law today, just moved: 80.22 was removed (eCFR shows Part 80 Subpart B "[Reserved]" since 2022-01-01) and the spec now sits in 40 CFR 1090.1550(a)(1): outside diameter "must not be greater than 21.3 mm" (= 0.839 in), checked in the eCFR current to 2026-10-30. https://www.ecfr.gov/current/title-40/section-1090.1550
  3. PEI letter (2007): the EPA rule is about leaded vs unleaded, not diesel; SAE recommends diesel spouts of 0.929–0.937 in. https://testing.pei.org/sites/default/files/tulsaletter/2007/05292007.htm

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