fuelComsumption.gs

var refuelingDateCol = 2;
var distanceCol = 3;
var oilingQuantityCol = 4;
var feeCol = 5;
var groupingMonthCol = 5;
var groupingDistanceCol = 6;
var groupingFuelConsumptionCol = 7;
var mySheetURL = 'http://your/form/url'

function myFunction() {
  var spreadSheet = SpreadsheetApp.openByUrl(mySheetURL);
  var sheet = spreadSheet.getSheets()[0];
  var lastRow = sheet.getLastRow();
  var dataCount = lastRow-1;
  var list = new Array();
  var consumptionList = new Array();
  var targetSheet = spreadSheet.getSheets()[1];

  for(i=2;i<lastRow+1;i++) {
    list.push({
      "date":sheet.getRange(i, refuelingDateCol).getValue(),
      "distance":sheet.getRange(i, distanceCol).getValue(),
      "quantity":sheet.getRange(i, oilingQuantityCol).getValue()});    
  }

  var i = 1;
  // Record fuel consumption per distance.
  UnderscoreGS._each(UnderscoreGS._tail(list), function(d) {
    var date = d.date;
    var fuel = d.quantity;
    var distance = d.distance - list[i-1].distance;
    var fuelConsumption = distance/fuel;
    targetSheet.getRange(i, 1).setValue(date);
    targetSheet.getRange(i, 2).setValue(distance);
    targetSheet.getRange(i, 3).setValue(fuelConsumption);
    consumptionList.push({
      "date":date,
      "distance":distance,
      "fuel":fuel
    });
    i++;
  }, this);

  var group = new Object();
  UnderscoreGS._each(consumptionList, function(d){
    var yyyyMM = Utilities.formatDate( d.date, 'JST', 'yyyyMM');
    if(UnderscoreGS._isEmpty(group[yyyyMM])) {
      group[yyyyMM] = new Array();
    }
    group[yyyyMM].push(d);
  }, this);

  var gi = 1;
  // Record fuel consumption per month.
  UnderscoreGS._each(group, function(a){
    var date = Utilities.formatDate( a[0].date, 'JST', 'yyyy年M月');
    var distance = 0;
    var fuel = 0;
    UnderscoreGS._each(a, function(b){
      distance += b.distance;
      fuel += b.fuel;
    }, this);
    targetSheet.getRange(gi, groupingMonthCol).setValue(date);
    targetSheet.getRange(gi, groupingDistanceCol).setValue(distance);
    targetSheet.getRange(gi, groupingFuelConsumptionCol).setValue(distance/fuel);
    gi++;
  }, this);
}