If you're looking to save money then it certainly helps to make sure that you're not paying over the odds for your fuel - especially as it's been rising rapidly over the last few months and now costs about 30% more to fill your tank each week.
I usually fill up at my local Asda, as it always has the cheapest petrol in the area and seems to drop it's prices before the others. The other two local petrol stations are a couple of pence per litre more, which isn't a big difference and not worth making a journey out of my way to fill up but I passed a petrol station this weekend that was charging almost 10p per litre more than what I was paying. That amounts to an additional £4-£5 every time you fill up. Multiply that over the course of a year and that's over £200 - just on fuel.
Check the Petrol Prices website for your local area.