QUESTION: 32mi/gal, 15m/mL, 6600yd/qt in order from least to greatest .
Using online conversion factors here: http://www.onlineconversion.com/
32 mi/gal (US) = 32 mi/gal (US)
15 m/ml = 15 km/litre = 35.3 mi/gal (US)
6600 yd/qt = 26400 yd/gal (US) = 15 mi/gal (US)
Ordering these fuel consumption rates from least to greatest,
6600 yd/qt (15 mi/gal), 32 mi/gal, 15 m/ml (35.3 mi/gal)