Is Sainsbury's petrol discount a good deal?

Sarah Coles
Sainsbury Petrol Station
Sainsbury Petrol Station

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?