The Commerce Commission has laid charges against the petrol company Shell over alleged breaches of the Fair Trading Act.
The 22 charges before the Wellington District Court relate to a product said to improve fuel economy.
The company is accused of making a false or misleading representation that its fuel economy formula petrol would have a more beneficial effect on fuel economy when testing showed the difference in fuel economy was on average 0.98%.
The charges relate to billboards in Wellington and Auckland, and brochures, posters and advertisements in newspapers and on television and radio.
Shell has already successfully defended the product against an Advertising Standards Authority complaint.
The case will be back before the court in June.