Does petrol consumption increase when I use air conditioner.My car is a Nissan...

[believer]

...Sentra 160si Year 2000 Model? I have been advised to refrain from using the heater because petrol consumption rises when the heater is on.

 

[nysenutz]

During city traffic....yes. On the freeway...no. Why? Because on the freeway you would have the windows down to cool the car, and the extra "drag" will make the engine work harder. The a/c always rips a few hp from the engine. And when you use it, there is an extra motor for your engine to operate. On long trips, be sure to turn the a/c off every hour or so and renew the fresh air inside the car. happy motoring.

 

[rocky]

Usually most cars will use more petrol with the air conditioner on as the engine needs to drive the air conditioning compressor to basically take the heat out of the air in the passenger cabin. However the fuel consumption could possibly be better with the air conditioning on than driving at speed with your windows open.
The heater shouldn't make any difference to your fuel consumption unless it is on working against the air conditioner.