Apparently there is a difference of up to 9c per litre for Petrol on the Island (all of which is the same product that arrives on the same tanker).

You can compare the prices that each Petrol Station is offering here:
http://www.datosdelanzarote.com/

Click on the link that says "Precios de los carburantes en las estaciones de servicio".

PCAN in Tias seems to be the cheapest.

Petrol prices overhere in the U.K. are £104p/ltr on average for unleaded.
Which works out at £4.68p/ gallon if your old like me!
I suspect our fuel may be manufactured by the same refinery,sold to the same supplier.shipped in the same tankers, but somewhere along the line it becomes "special" and leaps in value!! (my a**e)
Kinda takes all the fun out of putting your foot down.