i have to say that is some crap you are chatting about fuel mate! i only ever fill up at tesco, we are talking about road vehicles here.
Do you check your lap times round the local one way system on different types of fuel?
Or do you put your van on a dyno everytime you fill up?
are you on commision from shell, bp and esso for promoting their products againts any other fuel? this includes alternative fuels too
how many motorists fill up at supermarkets?
how many independants are going out of business?
have we some data on proven failures due to 'crap' supermarket fuel? apart from the unleaded saga.
One last thing, please can you inform the british rally that their selected control fuel is crap and that they WILL breakdown because of it?
As for having a tank, do you cover enough miles to make this viable? i think you get a very slight discounted rate but its not much. its more for convinience or companies using a lot of fuel, small savings soon add up when you are using lots. saves employees time as they can fill up at work - no sitting in a busy forecort or hiding in a layby for 20 mins

drivers dont need to handle cash or receipts and hopefuly fuel theft can be combated - get caught by the boss filling some cans for yourself and its down the road.
fuel cards are a handy way of employees buying fuel without having to have a credit card. normally have to give a vehicle reg registered to the card so again will help combat fraud / theft. some do deals on price but i would be supprised if there are massive savings