Hi Kev,
Well I use a slightly different method to calculate the MPG because it's difficult to know when you actually have a full tank. The neck of the tank can hold quite a lot of fuel and when you fill up the point of full depends on the efficiency of the pump’s cut out mechanism. You know that sometimes you can squeeze more fuel in than other times, just depends on the pump. Some don’t work properly and I’m sure we’ve all been covered in petrol before now.
So what I do is use the point at which the petrol light comes on as my reference which I think is more accurate than the fill up method and besides I never fill it up completely anyway because I’m too tight. So when the empty light comes on I fill up straight away with a set amount of fuel, record how much you spent and the price per litre and work out how many litres you pumped (if your receipt doesn’t tell you.).
When you know that, multiply the number of litres by 0.21997, this gives you the number of Gallons. Record your mileage or reset your counter when you fill up and record the exact mileage when the petrol light comes on again, this gives you the exact mileage you have covered since you filled up.
Once you have the mileage figure simply divide the number of miles by the number of gallons of fuel to give you the MPG figure.
Note if you don’t get to fill up immediately after the petrol light comes on keep a check on how many miles you cover on your way to the petrol station and estimate the likely additional fuel consumed for those few miles and include it in your calculation. However a couple of miles are unlikely to have a major affect on the MPG figure.
Hope this helps.
As a side note, my Picanto has covered 6600 miles now and I’m still only achieving about 47MPG at best, to my disappointment. Soundie…how many miles had you covered before you started to get over 50MPG?
Nick ;-)