The chain, which is the UK forecourt division of US-based Murphy Oil, has a network of 400 service stations in the UK.
It has been working with the symbol group since 1996, when it had only eight store sites in the UK.
It now operates 212 stores under the Costcutter banner, 30 of which are a supermarket format with the rest 'express' outlets. The deal is worth about £100m a year to Costcutter.
Murco general manager non fuel Tony Walker said: "The performance of our shops and their importance to the income of our business has grown rapidly over the past few years.
"Costcutter has worked with us to successfully grow our store numbers from eight to 212 and we believe this winning formula will continue to work.
"Throughout 2009 55 store refurbishments have already been planned, with the aim to improve store standards and imagery and extend consumer choice."