The offer of 50c-a-litre fuel has proved too tempting for many Queenslanders, with an estimated three kilometre line-up of cars banking up on a major road outside a service station south of Brisbane.

The Puma Energy at Woodridge in Logan offered the significant discount from 11am to 12pm on Friday as part of a promotion.

Bob Prasad, who owns MC's Indian grocer on Kingston Road, said he could see the "bumper to bumper" traffic banked up long past his business which is about a kilometre away from the service station.