Recirculated vs fresh air mode- what’s better for the engine?


Hi! My first time sending in a question:
I have a 2001 Toyota Camry. The question has to do with the air conditioner intake selector – my son says that using the “RECIRCULATED” mode is better to use than the “FRESH AIR” mode and is less stress on the engine. Is this true? And how would each mode affect the gas mileage?



The engine does not care what mode you use . I have no idea where your son got that idea and if there is a fuel usage difference it would be to small to measure.


Thank You!



Too much use of recirculate keeps moisture inside the car making it difficult to clear the windows of fogging up and leading to the growth of stinky mold in the hvac system.


Recirculated air is generally cooler than fresh air, the greater the temperature of the air passing through the evaporator core the greater the load on the system. A high load on the system means higher pressures for the compressor and a greater load on the engine.

In very hot weather I usually switch to recirculate when stopped at a traffic light, the outside air in a group of idling cars is 125 F plus. I switch to fresh air when moving, continuous use of recirculate will pollute the system and lead to foul odors.

By simply switching from fresh air to recirculate you will not be able to feel the difference in the load on the engine but when driving a car with a small displacement engine there is a noticeable difference in load between having the A/C on or off in 110 F weather.

Difference in fuel economy? You won’t notice with your old car but some late model vehicles change the A/C operation when “ECO” mode is selected so manufactures feel that there is a way of saving fuel with a reduced load on the A/C system.


Thank You!



Some vehicles have a humidity sensor inside the vehicle and a pollution sensor outside, when the controls are set to auto the system will switch from fresh to recirc accordingly.


Thank You.



It has been my experience that if the outside temperature is over 90ºF, you need recirculate to get the interior temperature down to a reasonable level.


I was in Reno, NV in July 2003. My 2002 Mitsubishi Eclipse. Outside air temperature was reported on the radio as 108F. My A/C switched itself to recirculate. I switched back to fresh air. It insisted on recirculate. When I got to my hotel I checked the manual. I found it was supposed to switch at 110F or over. Driving in traffic on hot pavement was no doubt over 110F.


Thank you, Bill.



Unless you’re driving in 100+F temps it makes no practical difference.


Thank you.



Re: the preference for using Fresh in most circumstances - our 2007 Town and Country’s HVAC automatically reverts to Fresh mode when the car starts if it was on Recirc when the engine was shut off.

Remember years ago all the small Japanese econoboxes you’d see in winter with the windows covered with frost on the inside? I surmise most of them were in Recirc mode. With or without AC, that means moisture buildup in the interior.


Different tolerance for different people. Having experienced really hot and humid. At 90F with tolerable humidity I would just have the car windows lowered. Many people here in the Pacific Northwest think they are dying at 80F. That is perfection for me and I am a native of the Northwest.


Thank you!



Jim, it is really not necessary to thank every post .


It really doesn’t make any difference. All recirculate does is shut off the outside air coming in. Use it if you are trying to maximize heating or cooling for a while, or if you are driving through an area with foul odors.


Thank you.



Not true, I use recirculating or max to dehumidify the interior. That is why the AC run in defrost mode.
Florida normally runs greater than 75% humidity, run on max until cold then adjust heat setting for cool, dry air.