# Fuel savers

I have been tracking my various cars’ fuel economy for 15 plus years now, using Excel. About six months ago I decided to go Mac and now have an iMac. I need as much help as I can get so I am a subscriber to your magazine. I have two points to make about your article.

Firstly, I keep a notebook in the car for logging fuel purchases and mileage at the time of purchase, and I always fill up to the maximum when to pump clicks. If I have to fill up in an ‘emergency’, I just put in, say, a nice amount such as 10 litres, which doesn’t go onto the spreadsheet – it gets added to the next full fill-up.

Secondly, in the spreadsheet I ‘smooth’ the miles-per-gallon figures using a ‘Running Mean Smooth’. One can choose the number of consecutive values to use their mean; I use four. So, the ‘current’ value on the chart is the mean of the last four figures. It makes trends easier to spot. I plot both raw and smoothed MPG values. Henry Chandler Alex Blake says… There are a few different ways to calculate your car’s fuel consumption, as you have rightly pointed out. The way in which you work it out depends on how stringent you want to be; whether you want to watch the pennies with an exact figure or get a more general idea of how much of a gas-guzzler your vehicle is. We just tried to keep it fairly straightforward this time!