[oldgreybloke]

I usually by fuel from Morrisons (I know, I know). However, before returning from Devon on Sunday I decided to give the old girl a treat and filled up with Vpower. Not only does it seem to run more smoothly and quietly, it used less fuel on the return journey despite similar conditions and weight. The fuel usage is objective but am I imagining the better performance (in order to justify the exorbitant cost perhaps)?

Use both sides of the paper and show your workings. Go.