A remaining fuel amount display device including: a fuel gauge; a sensor that detects the remaining fuel amount of the fuel tank; and an electronic control unit that calculates an indication value of the fuel gauge. The electrical control unit calculates the indication value by subtracting a subtraction value from a last indication value when the last indication value is greater than a detected value of the remaining fuel amount. The last indication value is calculated at one time before the indication value. The subtraction value is greater than a latest fuel consumption amount in an interval of the calculation of the indication value and equal to or less than a sum of the fuel consumption amount and a difference between the last indication value and the detected value. The subtraction value becomes larger when a value obtained by comparing the last indication value with the detected value is larger.

An idle stop condition determination method of an engine includes: calculating and storing a fuel saving estimation amount in idle stop of an engine on the basis of traveling information; calculating the amount of fuel consumption in restarting for restarting, when an idle stop condition of the engine is satisfied; comparing the magnitudes of the fuel saving estimation amount with the amount of fuel consumption in restarting, and stopping the engine in accordance with the result of the comparing; and restarting the engine, when a restarting condition of the engine is satisfied.

A material calculator for a truck to deliver a predetermined quantity of brine per mile driven by the truck for a known route of miles independent of and proportional to truck speed, wherein the truck carries a known number of gallons of brine and a known number of pounds of salt. The material calculator has a processor accepting entry values of route miles to be driven, number of times the route of miles is to be driven, number of gallons of brine carried by the truck, and the number of pounds of salt carried by the truck. The processor has software for calculating dispensing of the brine and salt so that each is exhausted when the route is completed. A hydraulic pump pumps hydraulic fluid to a variable flow positive displacement pump to implement the calculated number of gallons of brine per mile to be dispensed for the known route.