Does no climate control give you better mileage

Hello Prius people. While I have read in the past and it would make sense that turning off the heater and aircon would improve the mileage, I have not seen this. I have been experimenting and see no improvement. I have also read that if you do "vent only" this would also improve the mileage. How in the hell do you do "vent only"? The climate control is based only on the temperature you choose? Is there a button I am missing to bring the outside air in without heating or cooling it. Is "vent only" matching the outside temp w/ my climate control temp?

Thoughts?

 

<div class='quotetop'>QUOTE(sethkaufman @ Jan 22 2007, 12:48 AM) [snapback]378880[/snapback]</div>

Thanks for the info. I have only been driving in winter. (I have owned the car for only 2 months) and have not been cranking the heater much.

 

For Gen2 I don't think the AC has much effect on mpg as it is driven by the generator. In the winter, heat (or lack of) makes a BIG difference especially on short trips and the 1st 5 minutes. Some of us block the grill to keep the engine warmer. The colder the engine, the more it runs.

It finally got and stayed cold here. I dropped an average (per MFD) 1.5mpg on two short trips with 200+ miles on the tank. Two 35 mile commuting trips brought it up to -1mpg. I am still showing 50+mpg because of the blocked upper grill. Otherwise I'd be in the high 40's.

At outside temps over 50F I don't think it all makes much of a difference.

 

<div class='quotetop'>QUOTE(JimN @ Jan 22 2007, 05:55 PM) [snapback]379258[/snapback]</div>

I don't have any measurements, but even the Gen 2 AC unit is using power. It actually should be using more power than a regular belt-driven compression system given the conversion from IC to electrical and then back to mechanical work.

Of course, you are taking advantage of the batteries to avoid running the IC, but ultimately the IC has to recharge the electrical system.

I believe the only reason Toyota put in an electrical AC compressor was to avoid forcing the IC engine to come on whenever the compressor was called for. It was not an energy efficiency improvement in its own right.

 

My engine temperature, monitored via my ScanGauge, rises noticeably faster on these cold mornings when I leave the heat off. When the ICE is warm, its temperatures quickly drop when I run the heat while sitting still. I've seen it drop 10 degrees or more sitting at a stoplight.

I haven't done an MPG comparison -- with heat versus without -- but it seems clear to me that running the heat at certain times costs fuel economy; the ICE runs more when it's cool. So unless I absolutely need heat for comfort (I bundle up warmly) or to clear fogged windows, I run it only when the ICE is warm and has to run anyway (i.e., accelerating or cruising at 42+ MPH).

 

My Best Ever MPG (Over 10 Miles division) of 58MPG for 64 miles was with the A/C on. Way back with OEM tires, though.

I tend to warm the air in the car then turn the A/C off in winter. Long-term heating does occasionally reach a 10-MPG drop...

 

<div class='quotetop'>QUOTE(sethkaufman @ Jan 22 2007, 12:48 AM) [snapback]378880[/snapback]</div>

Turn on the AC/Auto, set the temp, bring up the climate display, look for the AC button to toggle AC on or off. When it's off, you are vent-only, at least as far as AC in hot weather. I don't know of a way short of turning the system off to avoid at least some heating in cold weather.

As to thoughts, I thought cabin heat and cooling was also heating and cooling the battery, so that it was better to just get in and drive and not worry about it too much. I do find that on some sunny days with cold temps, 65 is still too hot.