1. Because it is a very high individual cost item within the total cost of vehicle operation.
2. Because it is an area which is susceptible to fiddling by drivers and others.
3. Because high fuel consumption can be an indication of a number of important factors:

(a) Malfunctioning of the engine,
(b) Drivers fiddling with the fuel pump on diesel vehicles to gain more power or more speed (This can result in
the emission of black smoke - a serious offence punishable by prosecution and by prohibition of the use of
the vehicle for a period),
(c) Drivers selecting routes, which are not the most direct, for their own ends (to visit particularly favourite cafes
for example).

Recording fuel issues Fuel costs are dealt with relatively easily for costing purposes, subject to one important provision. This is the need for the utmost vigilance in faithfully recording fuel issues to each vehicle whether these issues are from the operator's own bulk storage tanks or from retail garage pumps. Drivers should be encouraged to record accurately their fuel drawings both at home and when away. Garage receipts usually provide an adequate record for retail purchases, provided the driver does not lose the receipt but more difficulty is likely to be encountered with supplies drawn at base from bulk stocks.

Among the methods available for recording fuel issues to individual vehicles by far the most effective is the pump that only operates when. a special magnetic card or key is Inserted. Once the card is inserted into the pump the driver serves himself with the required amount of fuel and, most important, the metering device records exactly how much fuel was issued and the code number of the card used. Consequently, when the print out is taken from the pump a detailed record of issues to vehicles is available.

In the absence of any fuel recording system as sophisticated as this one the next best choice is a conventional meter pump that indicates gallons and tenths. Reliance is then placed on the driver or pump attendants to record the issue accurately as to quantity, vehicle number and date of issue on a form.

At this point the system falls down if for some reason a recording is not made - a frequent occurrence if drivers are in a hurry, perhaps because they are late getting away on a journey, in a rush to get off home at night, or if they have to stand in the rain to refuel. Worse even than this is the bulk supply system that has a pump with no metering device. Whatever the excuse, one missed recording of 100 or 150 litres of fuel in a week destroys any hope of achieving accurate fuel consumption analysis and accurate running costs.

Mileage recordings Equally important is accurate recording of the mileage covered by vehicles. Legal requirements ensure that vehicles have speedometers and that generally they are kept in working condition.
They do occasionally cease to work because of cable breakages or other faults and drivers, too, fail to submit readings at regular intervals despite there being a provision on their record sheets for start and finish readings to be shown.

Calculation of fuel costs Given that both fuel issues and mileage readings are accurately recorded, the rest is easy. Over a period of, say, one week a vehicle draws X amount of fuel and covers Y kilometres. The amount of fuel in litres multiplied by the cost of the fuel per litre provides the cost of the fuel consumed in the week. Division of this figure by the mileage covered provides the cost of fuel per kilometre.

Example:
Fuel drawn = 400 litres
Mileage covered = 1,200 kilometres

Cost of fuel:

Bulk supplies = 300 litres at K89.59 = K26,877.00
Retail purchases = 100 litres at K94.30 = K9,430.00
      Total = K36,307.00
Fuel consumption: (1200 kilometres)/(400 litres) = 3 kilometres per litre
Cost of fuel per kilometre: (K36,307.00/1200 km) = K30.25

So far as actual fuel consumption is concerned in kilometres per litre this example of a one week analysis is not sufficient to show a long term accurate performance for the vehicle.
The 1,200 kilometres covered that week may have been mainly on motorways or conversely it may have all been on relatively congested urban roads. Routes may have been particularly hilly or alternatively all on the flat. The vehicle may have been fully loaded over most of the distance or only partly loaded for half of it and the rest empty.
It would not be fair to judge fuel consumption on so small a sample of activity, so to obtain more accuracy the figures should be examined after say 3 or 6 months.
But for the costing exercise the weekly figure is satisfactory because, whatever the fuel consumption in kilometres per litre, the basic cost criteria remain unchanged i.e. the amount of fuel used, the cost of the fuel and the mileage covered by the vehicle.