This site describes solve-engine as it is on main: 2.43.0, which npm does not have yet. npm installs 2.40.0, so a page may show an answer that version does not give yet.
FUEL_PACKAGE
const FUEL_PACKAGE: IEnginePackage;Defined in: packages/engine/src/packages/fuel/FuelPackage.ts:11
Fuel economy (issue #190): the abbreviations mpg and kmpl, and the
reciprocal conversion between distance-per-volume (miles per gallon, km per
litre) and volume-per-distance (litres per 100 km). The reciprocal itself
lives in the unit converter; this package just teaches the abbreviations. On
by default and removable.