Is Sainsbury's petrol discount a good deal?

Sainsbury's is offering 11p off a litre of fuel to its mobile phone customers. To get the deal, you need to top up a Sainsbury's mobile pay-as-you-go phone with £10. In return you'll get 11p off a litre of fuel. This works out as a saving of almost £7 on a typical tank of fuel.

So is this a decent discount?

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