A rise in retail petrol prices on Thursday has generated renewed complaints about the entire system of fuel taxes.
The rise was pushed in part by a rise in excise by 3 cents per litre.
That increase applies to petrol driven vehicles, while a separate rise put road user charges for diesel vehicles up by 5.9%.
Motoring journalists John Oxley and Dave Moore said the distinction is messy, convoluted and arcane.
The Automobile Association is also critical of the current system.
The Ministry of Transport reviewed the matter five years ago and resolved to retain the petrol tax-road user charge distinction, because a lot of diesel is used on farms, which should not be taxed to pay for roads.