An engineering specialist has endorsed advertising claims made by Shell relating to its fuel economy additive.
Shell is before the Wellington District Court defending 22 charges laid by the Commerce Commission under the Fair Trading Act.
The 2006 advertising campaign said the fuel additive was designed to take motorists further.
But the Commerce Commission claimed it was misleading, because using a tank of the fuel increased the distance travelled by less than 1%.
Professor Harry Watson from the University of Melbourne told the court on Wednesday that Shell's fleet testing of the product met international standards.
He said improvements in fuel performance occur incrementally and are difficult to achieve and Shell had proven its product delivered a fuel economy benefit.
