The legal requirements for fuel quality, and your rights when buying fuel such as diesel or petrol.

Service stations must not mislead on price

When you buy petrol or diesel, you have rights under the Consumer Guarantees Act (CGA) and the Fair Trading Act (FTA).

The FTA applies so that companies can’t misrepresent the qualities of fuel, eg it’s illegal to sell petrol labelled as Premium Unleaded when it’s really Unleaded 91.

Petrol prices are not regulated by the government, but shop around for the best price when buying fuel. Most service stations have days when fuel is cheaper. Service stations must not make false or misleading claims about their prices under the FTA either.

This means the price listing should be the same:

  • On all outdoor signs.
  • At the pump.
  • At the cash register.

The government does monitor petrol stations for fuel quality and compliance with the Engine Fuel Specifications Regulations(external link) . These regulations govern important properties of petrol and diesel, to protect people and the environment.

Know your rights

Your rights under the Consumer Guarantees Act mean that fuel bought for your personal use must be:

  • Of acceptable quality.
  • Fit for purpose.
  • Free of minor defects.
  • Safe.

If these minimum guarantees aren’t met, you should go back to the petrol station and ask for a remedy that includes repairs, exchange or a refund.

Under the Fair Trading Act, you have protection from:

  • False or misleading representations or statements about the fuel or petrol prices.
  • Unsubstantiated claims that have no basis in fact.
  • Unfair sales practices.

See also:

Fuel quality

The Engine Fuel Specifications Regulations(external link) describe the most important performance properties of your fuel, such as the octane number. They also specify limits for components that could harm you, your vehicle or the environment.

Monitoring scheme

Under the national fuel quality monitoring scheme, Trading Standards (part of the Ministry of Business, Innovation and Employment) organises testing of petrol and diesel samples to ensure fuel companies are complying with the regulations. Approximately 30–40 samples are tested each month.

Motorists fund the fuel quality monitoring scheme through a small part of the petroleum fuels monitoring levy.

A small number of samples may fail because the fuel has been contaminated somewhere along the distribution chain. For example, some diesel may have mistakenly been put into a service station’s petrol tank.

Accuracy of petrol pumps

Trading Standards appoints Accredited Persons to check that fuel pumps are accurate under the Weights and Measures Act. A certificate of accuracy will be issued and a small adhesive label placed on the pump where you can see it.

While car manufacturers’ stated capacities for fuel tanks are not precise measurements, petrol pumps are calibrated measuring instruments, so they may differ. Also, the design of car fill pipes allows fuel or vapour to sometimes shut off the petrol pump nozzle at an early stage in the fill.

It is safer not to fill the petrol tank right to the top, as petrol will expand – due to the temperature in the car being higher than that in the underground storage tank.

All petrol pumps must be certified accurate.


You should always:

  • Check that the price on the pump matches the price on the sign.
  • Make sure that the pump is set to zero before you start.
  • Remember the pump number and price so the cashier doesn’t charge you incorrectly.
  • Check your receipt.

Although petrol prices are not regulated, petrol stations can’t get together to fix prices so that there is no competition within a local area. Price-fixing is illegal under the Commerce Act(external link) .

Read more about petrol pricing(external link) on the Commerce Commission's website.

If things go wrong

If you think there's a problem with your fuel:

  • Contact the service station —they should investigate your complaint. This might involve testing the fuel involved and letting you know the result.
  • Complain to Trading Standards — they will follow up with the oil company, but will not take direct action on your behalf.

How to complain

Complain to Trading Standards(external link)  — Trading Standards

More help

Get support at any point from:

  • Citizens Advice Bureau (CAB) — a free, independent service, run by volunteers. CAB can advise you on your consumer rights and obligations, in person, by phone, or online.
  • Community Law Centre — offers free one-on-one legal advice to people with limited finances. The organisation has 24 community law centres throughout the country. You can find legal information and other resources on its website.

Find a CAB(external link) — Citizens Advice Bureau

Our law centres(external link) — Community Law Centres

Common situation


Jack notices all the petrol stations locally are charging exactly the same prices for unleaded petrol for the month of September. He finds this odd and contacts the Commerce Commission to report it. The Commission may choose to investigate whether the petrol stations have got together to fix prices.