Hi Ratchet.
I topped up the 406 today, first time since putting in the Super Diesel and returned 45.5 mpg just 1.3 mpg better than the standard stuff, not a lot but I reckon it works out slightly cheaper, however the improved performance has convinced me to carry on using it. I buy it at Tesco's, they sometimes give a 5p a litre off if you buy enough shopping to feed the 5000.
Bryan