Australia Post is planning to reduce its fuel bill and carbon emissions by switching its corporate car fleet to fuel-efficient Toyota vehicles, especially the hybrid Prius.

One of Australia's largest employers, Australia Post has close to 1,000 sedans, wagons and utes in its corporate fleet.

It has signed a two-year contract to purchase vehicles from the Toyota range including Prius, Yaris, Corolla and Camry - all of which use less fuel and produce fewer emissions.

Prius is rated at the top of the Federal Government's Green Vehicle Guide with five stars. All Yaris models have four-star ratings, Corolla 3.5 or 4.5 stars and Camry 3.5 or 4 stars.

Toyota Australia's corporate manager of national fleet Deborah Bacon said Prius would make up more than 60 per cent of Toyota sales to Australia Post.

"By replacing its vehicles with Toyota cars, Australia Post has the potential to make substantial savings on fuel costs and reduce its carbon dioxide emissions by hundreds of tonnes a year," Ms Bacon said.

"For every Prius they buy, Australia Post will save at least $2,340 a year on fuel compared with their existing large petrol cars and more than $700 a year compared with their large LPG vehicles," she said*.

"Prius also emits less than half the carbon dioxide at just 106 grams/km - the lowest of any car on sale in Australia - and consumes just 4.4 litres/100km.

"Camry is the only four-cylinder car built in Australia while Yaris and Corolla are also extremely fuel-efficient," Ms Bacon said.

In addition to the fleet deal, Australia Post managing director Graeme John AO has chosen a Prius for his personal car.

Australia Post's group manager corporate public affairs Stephen Walter said the Toyota purchases - as with all significant outlays - had undergone environmental, economic and other assessments.

"The decision by Australia Post to buy Toyota cars is an important milestone in our commitment to cutting fuel use and greenhouse gas emissions," Mr Walter said.

"We take great care when selecting new vehicles to ensure they will enhance our environmental performance - and that is why we have signed up with Toyota.

"We recognise the threat of climate change and we are committed to continually improving energy efficiency and reducing our impact on the environment.

"This includes introducing new technology to the fleet and continually upgrading our vehicles to the latest environmentally efficient technology."

* Figures based on ADR 81/01 combined cycle for fuel economy, 91RON unleaded fuel at $1.60 a litre and LPG at 65 cents a litre with an average travel per car of 26,000km a year.