Does a faulty exhaust effect fuel efficiency in a petrol car?

Question

I've had a hole in my exhaust for a while (it's very loud), and I'm sure I'm having to fill the tank up more often.

Answer 1

It is possible. Many newer cars use sensors in the exhaust to adjust the Fuel/Air ratio. So, if there a leak or something in the exhaust it may give the sensor a false reading. This may cause the car to run "Rich" too much fuel, which in turn increases fuel consumption.

Answer 2

an engine has to have a certain amount of back pressure .if you cool the motor too much then it wont run right because your cooling the valves too much.