Redmires wrote:What's with the rolling eyes then ?
.... I record the mileage and fuel (brim to brim calculation) every time I fill up and produce stats and graphs with the figures. ..
If I may but in, the fact that it's a "brim to brim" amount makes little difference. The accuracy is in simply recording total miles and total fuel.
Brim to brim simply makes it easier to track seasonal changes, the likes of my flat tyre and makes the math/maths easier. Divide one by the other, you get mpg or in English miles per gallon.
It's simple math/maths that school children are taught.
Because I don't use brim to brim, my math/maths is slightly more complicated in that I use a historic rolling average to get rid of quantisation* effects. That is to say I divide the distance over the last three petrol stops by the amount of fuel added in those three stops, which I try to keep constant.
*The effect of the fact that we work on descrete data that we gather each time we refuel. The same effect is what causes inaccuracy in the instant readings of fuel consumption on computer dashboards. Errors in reading very small amounts of fuel lead to the dash giving wrong reports, but it should be used as just a rough guess when looking at a dashboard instant value.