The pair have so far made it more than 1,000 km from Sydney to Brisbane, the capital of the northern Queensland state, in a vehicle which can use both diesel and vegetable oil.

"There's a solenoid in there that switches between the diesel and the vegetable oil," Gerard Mimmo told the Brisbane Times newspaper. "With a cold engine you have to start with diesel. Once it is up to running temperature then you can switch over."

He said the couple hoped to have a carbon-neutral honeymoon, relying on donated oil from truck stops and fish and chip shops, by using solar power and biodegradable products, and by staying in bush camps and buying locally produced food.

He said they would buy carbon credits and fund tree planting to offset any carbon pollution, to ensure their honeymoon is carbon-neutral.

Progress of the trip can be followed on the Around Oz on a Battered Fish Website at www.ozonabatteredfish.blogspot.com/.