Citizen E610 Instruction Manual page 97

[Calculation of fuel consumption]
Q : How much fuel is needed for a vehicle to run 5 hours if the fuel consumption
rate of that vehicle is 7 liters per hour?
A : Align 70 of the outer scale with the "  " of SPEED INDEX of the inner scale.
Result: 35 liters - 35 corresponds to 5.
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