Turn Off A/c To Conserve Fuel - What's The Climate Control For?

japthree · May 29, 2008

It is recommended to switch off the air-con to conserve fuel; if you set the climate control temp to the lowest/coldest setting (16) with A/C off it doesn't feel as 'cold' and doesn't really help in hot weather? So what's the trade-off? A/C off or on?

maneesh · May 29, 2008

climate control without AC on is just regular heating and ventilation. it's only if you use a/c too, then your fuel consumption suffers by 1 or 2mpg.

sparkystav · May 29, 2008

Your ment to use AC on hot or cold to "clean" the air and the system

Noel · May 29, 2008

turn off the AC and drive with the windows open ... ( i'm jesting, windows open would waste more fuel)

I didn't notice any difference in MPG or performance when i tried not using it for a few weeks... but boy did it smell for ages after i started using it again...

The Transporter · May 29, 2008

As has been said, the climate control with the AC off is simply an automatic heating system, the system will do what it can to maintain the set temperature in the car but with the AC off and no refrigerated air entering the HVAC system then what it can do is limited.

Refrigerating the air does a number of things, most noticeably it cools the air to just above 0 centigrade, It also removes a large amount of humidity from the air which on close, "Muggy" days is a relief, Dust and other particles which find their way through the pollen filter will also be further filtered when they stick to the damp evaporator coils. The HVAC system will then direct the air to the vents, or heat a portion of the air and blend it with cooled air to maintain the set point as is directed on the controls... The Lex also has a Solar radiation sensor on the dash which will cause the vents to blow either cooler or at a higher volume of air to compensate for solar gain through the glass which make you feel warmer than the cabin temperature actually is... you may notice this as you drive in to a shaded area, the vent temp/ volume of air (Fan speed) will change

By modern standards the IS200 HVAC system is pretty old fashioned but it is superior to any over engineered European system when the heat is really on.

Windows open or AC on? Generally speaking below 40mph it is cheaper to drive with the windows open but as speed increases, open windows add more and more drag to the point where it is more cost effective to use the AC

Gareth Rose · May 30, 2008

The Lex also has a Solar radiation sensor

So is that the other little dome by the sensor for the lights. I wondered what the extra was for.lol. I bet il be noticing it everytime I go into the shade now.lol.

Rob's Lexx · May 30, 2008

The Lex also has a Solar radiation sensor

So is that the other little dome by the sensor for the lights. I wondered what the extra was for.lol. I bet il be noticing it everytime I go into the shade now.lol.

does that effect with the solar sensor only occur on 'auto' vent function?

The Transporter · May 31, 2008

The Lex also has a Solar radiation sensor

So is that the other little dome by the sensor for the lights. I wondered what the extra was for.lol. I bet il be noticing it everytime I go into the shade now.lol.

does that effect with the solar sensor only occur on 'auto' vent function?

If the fan speed is on a set speed, then the only other thing that the HVAC can do is to drop the vent temperature but whatever the set point, it will try to drop the cabin temperature by a degree or two.

To be honest I find this feature, and automatic temperature control in general to be annoying and I much prefer the manual air con on my van, but as I said, any Toyota/ Lexus AC, especially the fixed displacement compressor systems will leave any European car for dead when it gets hot but not so good on cool, humid days as the compressor does cycle on and off a bit too often

WylieCoyote · May 31, 2008

I've done countless tests in every one of my cars - AC on, AC off and compared fuel economy. I can say, hand on heart, I've never noticed a scrap of difference. And, what's the point in buying a nice car if you don't play with the toys just to save fuel - if that's what's important, buy a bicycle!!!

tHomBleached · June 1, 2008

I've done countless tests in every one of my cars - AC on, AC off and compared fuel economy. I can say, hand on heart, I've never noticed a scrap of difference. And, what's the point in buying a nice car if you don't play with the toys just to save fuel - if that's what's important, buy a bicycle!!!

Couldn't agree more! I keep my A/C on all year round, that way I never turn up to meetings with big ol' M25-stressinduced-sweatpatches.

Had the unfortunate displeasure (sorry 250 owners) over driving a 250 and a 220 while my baby was being serviced and the only redeeming feature that I liked about it (about from the ML sound) was the pleasent sensation of having air-conditioned air blowing around the family jewels

black 300sport · June 1, 2008

I do the same 48 mile trip to work every day and as we al do get board,iv tried air con on,air con off and climate control on auto.Like people are saying it really make very little differance to the fuel econ.For me its more the mood im in,do i fancy warm sunshine with the sunroof and windows open,or nice cool quite air-con.