Which brands of Diesel and Petrol do you find best for quality and MPG ?

Hi there,
Got half a tank of diesel from <snip> in my pathfinder and noticed engine rumbling as if fuel is not reaching to injectors properly. In mornings when engine was cold car cuts out. On Wednesday the 24th of February i filled half of a tank from <snip> and with in half an hour all hell broke lose. Every time i took my leg off accelerator car cuts out. From Douglas, work is only 15 minutes and my car cuts out about 10 15 times. Engine started rumbling and on every RED light it stalled. Explained to my mechanic and before i finished explaining the problem he said its DIRTY DIESEL and he has about five customer recently with same problem. Any ways gave him my pathfinder and he had to clean fuel tank, fuel lines, EGR valve and replace the fuel filter. Half a tank of diesel was drained as well. Took couple of hours to do the job and he said that he found dirty BROWN stuff in fuel tank which was the cause of last few fuelling. It made a hole in my pocket when i paid 260€ but my car is cruising like a 747. MPG is gone up, engine is smooth, acceleration has improved BIG TIME.
Is there any way of making a complain about the **** fuel those two garages are selling i.e <snip> and <snip> (May be more garages are doing the same). There must be a petroleum agency who carries out fuel auditing time to time. What ever happen guys just avoid two garages above and please share the garage name if anyone of you had the same experience.