Garmin APOLLO GX65 - Manual (Page 176)

Fuel Measure
The GX50/60 allows you to choose the units of
measure for your fuel displays. Fuel units may be
displayed as US Gallons (USG), Imperial Gallons
(IMG), Liters (L), Pounds (LBS), or Kilos (KGS).
Fuel Measure
usg
US Gallons
Press SEL to enable selection. Turn the SMALL knob to
choose the desired units and then press ENTER .
7-24
System Functions
SEL
ENTER