In cells A5 and A6 just put the one-way distance to the away station. The spreadsheet automatically calculates the round-trip cost.
Tested in Excel, OpenOffice Calc and Gnumeric.
|15||tank size (gallons)|
|29.55||miles per gallon|
|3.619||local price per gallon|
|3.599||away price per gallon|
|2.00||miles to local station (one way)|
|5.00||miles to away station (one way)|
|=A1*A3||cost to fill up at local station|
|=A1*A4||cost to fill up at away station|
|=A8-A9||savings from cheaper gas|
|=(A6-A5)*2||extra round trip distance to away station|
|=A12/A2||extra gallons to drive to cheaper station and back|
|=A13/A3||extra travel cost to away station (based on local gas price)|
|=A16/A1||savings (loss) per gallon|