Fuel consumption log book is a way of keeping your fuel compsumption record for your car. It's very important to monitor how your car burn the fuel. From this, you can know whether your car is normal or not. Is it something wrong with the engine or not. And it also can be your health record for your car.

For this purpse, I am using OpenOffice spreadsheet to record the data for my fuel consumption. I start record my fuel consumption since I bought my car in Feb 2008. The most important thing here is the mileage streched (in kilometer) for a liter of petrol. Since our fuel price is subjected to change. So kilometer per litre is the most effective measurement for us can monitor.

The attributes I recommend to monitor are as follows :

1) Date of start filling the fuel until date of re-fuel.
2) Brand of petrol station.
3) Litre of the fuel.
4) Price of the fuel (RM).
5) Distance in kilometre.
6) Sum of kilometre per litre.
7) The current price
8) Notes.

The method I used to calculate my fuel consumption is when my fuel indicator bar show only one bar left, I will reset the trip meter and start to re-fuel. Then I will record the start date and litre of the re-fueling. For the end date, I will state XX first. And I will write down the date when I re-fuel my car. Then I drove the car until the indicator car is one bar left again. So soon before I start to re-fuel, I will record the mileage of the trip meter.

The kilometre per litre then was calculated as follows :

fuel consumption = (kilometre of the trip meter) / litre of the fuel

Then I will get how far my car can go per litre of petrol.

For the first example, you can see that there is a red indicator means that my fuel consumption is quite poor. My car only can manage to go for a 13 kilometre with a litre of petrol. Then you can see that after the red indicator, we can see in the NOTES section written that after the car has undergo a service for a 5000KM, the fuel consumption is good again.

In the second example, we can see that in the long distance journey using highway, the fuel consumption can stretched up to 19 kilometre per litre. And as it approaching the service period, the fuel consumption is decreasing again. Means that the viscosity of the engine oil is affecting the car mileage.

As I am using Semi-Syn Petronas Syntium 800 15W-50. So I have to flush the engine oil every 5000KM interval. As you can see in the notes section, for the service at 15,800 KM, I also record the items that has been replaced. The engine oil, oil filter and etc.

Before this I always shift my gear at 2500RPM or below. So I start experimenting what happen to the fuel consumption when I practicing shifting gears above or at 3000 RPM? As you can see, the fuel consumption is quite bad isn't it?

So this is the example how a fuel consumption log book can help you monitoring your car condition.