mpg shows 47 but doesnt change

[3rensho]

Trevor has you covered. If the 47 mpg is the average over many thousands of miles it would take a huge change to alter the value over a short time/miles driven period. I reset mine about every 5-6K km just to get a feel for what is currently happening. It starts higher and then eventually settles down to 5.8l/100km and stays there until the next reset.