The AA says drivers can save up to 40 per cent on fuel costs by reducing their speed.
Green Party leader Eamon Ryan has suggested slowing down to make petrol or diesel go further.
Paddy Comyn from the AA says it can actually make a big difference:
"Certainly in the car that I've been driving, I've seen quite a significant reduction in the fuel economy as much as 40% between 100 kilometres per hour and 120 kilometres per now, in a different car you will get a different result but the general rule of thumb is that you will save your fuel economy by 20% If you do that speed reduction."
