Originally Posted by Ti Rich
You really need to manually check the MPG as tuning boxes effect the way the MPG is calculated by the ECU. Chances are the MPG will be worse when ypou manually calculate it.
I'm definitely using less fuel. The week before I deliberated on which choice to go for, I got the trip computer to 0 miles before sticking £40 in. That week, the car returned 39.9mpg. I did the same last week - yet I still had 38miles remaining and 44.1 mpg.