Research at the US Agriculture Department of Agriculture has raised the possibility of using vegetable oil as an engine oil additive.

The research has centred on altering the chemical structure of vegetable oil to make the molecule more resistant to temperature change.

Scientists have increased the temperature durability and shelf life of soybean oil by reducing the amount of double bonding in the molecule.

"This is not going to replace conventional oil or anything that is going to be burned in the engine," said a research team spokesman. "It has shown signs of great potential in use not as a sole fluid but as a complement with existing engine oil."