Motorists are being advised by the Energy Efficiency and Conservation Authority (EECA) against using the slipstream of other vehicles in an attempt to save fuel.
Some drivers have said they do this but EECA general manager Liz Yeaman said it was neither effective nor safe.
"There are a lot of people who try and keep close behind the car in front because they think they'll be in the slipstream," Ms Yeaman said.
"Actually all that happens is that they end up having to brake a lot of the time and, whenever you have to brake, you're losing energy that you've invested in keeping yourself going."
This summer, the authority is promoting six fuel-saving driving tips such as driving at the speed limit, avoiding idling the engine, and taking corners smoothly without heavy braking and acceleration.
The authority is also urging people to drive carefully as the best way to save money on fuel.
People should not drive slowly and hold people up but instead stick to the speed limit, Ms Yeaman said.
If people were stuck in traffic for more than 30 seconds, they should turn their engines off because it did not take much fuel to restart a modern car, she said.