Well I've just read that turning on the air recycling switch to 'on' will improve fuel economy! Any truth in this ? 

The car doesn't have to run the A/C compressor as much because it is keeping the air in the car cool, not having to keep cooling the air coming from outside.

Cars with auto A/C will usually use recirc initially to drop the inside temperature quicker, before switching to allowing outside air in.

It may do but it is academic if you crash the car because of the lack of oxygen, fumes being recirculated or the windows steaming up. In these cases it is also academic that your electrics might also suffer from damage due to the moisture in the air condensing on them. 

I have witnessed a practical demonstration about how quickly oxygen is used up in an enclosed space, not a car but the principles are the same. 

19 minutes ago, Tizer said:

 I have witnessed a practical demonstration about how quickly oxygen is used up in an enclosed space, not a car but the principles are the same. 

As a kid we used to see who could stay inside a sleeping bag the longest before nearly passing out! 🥵 🙄  🥴

My first car was an ancient Mini. I was lucky it came with a heater - they were an option new - but that was recirculation only. It got unpleasantly hot very quickly and steamed up so fast you had to drive with the windows open which rather defeated the object.

My next car was a Mk 1 Cortina with the airflow ventilation which was a revelation!

8 hours ago, Ian Lanc said:

Well I've just read that turning on the air recycling switch to 'on' will improve fuel economy! Any truth in this ? 

In theory, certainly.

But if you're getting into a hot parked car with the temp outside say 25 deg, the inside will likely be 35 deg due to the greenhouse effect. So in that case, I would NOT use the recirc button until the temp inside the car has dropped to the same as the outside temp.  In practice, I drive for a few minutes with the windows wide open to expel that greenhouse heated air and THEN think about putting the aircon on.

7 hours ago, Tizer said:

It may do but it is academic if you crash the car because of the lack of oxygen, fumes being recirculated or the windows steaming up. In these cases it is also academic that your electrics might also suffer from damage due to the moisture in the air condensing on them. 

I have witnessed a practical demonstration about how quickly oxygen is used up in an enclosed space, not a car but the principles are the same. 

All of that is academic seeing as the cabin isn’t airtight.

The recirc system switches on an electric motor.

electric motors use energy.

The energy needs to be regenerated and put back into the battery.

Question is - would you even notice the difference?

7 hours ago, RMurphy195 said:

The recirc system switches on an electric motor.

electric motors use energy.

The energy needs to be regenerated and put back into the battery.

Question is - would you even notice the difference?

The AC uses the same fan.