How to Keep a Fuel Expense Log: A Simple Method That Shows Where Your Money Goes

Most people have only a rough idea of how much they spend on fuel. They know how much they paid at the last visit and little more. A fuel log changes that. It takes about a minute each time you fill up, and in return it tells you your real mileage, your true monthly cost and whether your vehicle is slowly getting worse. You can keep it in a notebook, in a phone note or in a spreadsheet.

What to record at every fill-up

Write down five things each time you buy fuel:

1. Date.
2. Odometer reading in kilometres.
3. Litres added. The pump receipt shows this. If you ask for a fixed amount in rupees, divide the amount by the price per litre.
4. Price per litre, which lets you see how prices change over time.
5. Total paid.

Add a note when something is unusual, for example a long highway trip, a heavy load, a new tyre or a service. These notes explain changes in the numbers later.

The full-tank method

For an accurate mileage figure you need to compare like with like. Fill the tank completely each time, stopping when the pump clicks off, and record the litres. The mileage for the previous period is:

Kilometres since the last fill divided by litres added now.

For example, suppose the odometer read 12,000 km at the last full tank and reads 12,420 km now. You add 10.5 litres to fill the tank. The mileage is 420 / 10.5 = 40 km per litre. If you ever skip a fill or fill only partly, the next calculation will be wrong, so wait for the next full tank before you compare.

Work out the cost per kilometre

Divide the total you paid by the kilometres covered. If those 10.5 litres cost Rs 4,200 for 420 km, the cost is Rs 10 per kilometre. Over time you will see how this number moves with the price and your driving.

A simple table you can copy

Draw columns in a notebook or spreadsheet with these headings: Date, Odometer, Litres, Price per litre, Total paid, Km since last fill, Km per litre, Rs per km, Notes. In a spreadsheet, the last three columns can be formulas. For example, Km per litre equals the distance column divided by the litres column. At the bottom of each month, add the litres and the money, and divide total distance by total litres for a monthly average, which is steadier than any single fill.

What the numbers tell you

• Your true monthly cost. Add all totals for the month. This is the number to use when you plan a budget, and it may differ from what you guessed.
• Your average mileage. Use it with our fuel calculator to estimate trips and to compare vehicles.
• A trend. A slow fall in kilometres per litre over several months points to a developing problem, such as low tyre pressure, a dirty air filter, a worn chain or an engine that needs tuning.
• The effect of price changes. If you record the price each time, you can see exactly how much more you paid after a rise.

Spotting a problem early

Suppose your car averages 12 km per litre and one tank gives only 9. Before you blame the pump, check what was different. Was it a day of heavy traffic, a long air-conditioned drive, a new load, or a different pump? If the next tank is also low, look for a cause. A sudden big fall can mean a mechanical fault, while a sudden big rise can mean that you filled partly or that the pump gave short measure. Our article on what to do if a pump overcharges you explains how to check.

Use the log to test changes

The log is the best way to learn whether an idea works. If you raise your tyre pressure to the recommended level, change the air filter or start driving more smoothly, compare the average over the next few tanks with the average before. One tank is not enough, because many things vary. A month of records gives a fair answer. Read about the checks in our guides to tyre pressure and fuel-efficient driving.

For drivers who work

If you earn money with your vehicle, add two more columns: fares collected and other costs. Then you can see your real daily income, as we explain in our guide for rickshaw and Qingqi drivers. Records are also useful if you ever need to show your expenses to an accountant or tax office, though you should check the rules that apply to you.

Keep it simple

The best log is the one you actually keep. Some people photograph every receipt and enter the numbers at the end of the week. Others keep a small notebook in the glove box or the bike's storage compartment. Do whichever is easiest. If you miss a fill, simply carry on, and mark the gap so you do not calculate mileage across it.

Frequently asked questions

Do I need an app? No. A notebook is enough, though a spreadsheet saves the arithmetic. Many free apps also exist, but check what data they collect before you use one.

How long before the numbers are useful? After three or four full tanks you have a reasonable mileage figure, and after a month you have a monthly cost.

What if the odometer is broken? Use a trip meter or a phone application that records distance, and keep to the same method.

Start with your next fill-up. Compare your result with the current price in our price table, and read our guide to fuel prices in Pakistan to understand the changes behind the price you pay.