Gas Mileage And Climate Control

[rocky2]

We notice the same thing others have notice regarding the gas mileage going down recently, most believe because of the cold.

We were consistently getting 27+ until recently. That was with AC off.

Since winter our mileage has dropped into the 23 mph range or less.

Just noticed with “auto” climate off mileage jumps back to 27+.

With “auto” climate switched on we notice we can barely keep the engine off.

With “auto” climate off we can keep engine off up to 40 mph like we were able to in the summer.

What give?

[jashev]

We notice the same thing others have notice regarding the gas mileage going down recently, most believe because of the cold.

We were consistently getting 27+ until recently.  That was with AC off.

Since winter our mileage has dropped into the 23 mph range or less.

Just noticed with “auto” climate off mileage jumps back to 27+. 

With “auto” climate switched on we notice we can barely keep the engine off.

With “auto” climate off we can keep engine off up to 40 mph like we were able to in the summer.

What give?

←

I have noticed that the A/C light stays on as long as the system is set to auto climate. When you use the manual adjustment, you can shut the A/C down and that seems to help.

[patt]

I have noticed that the A/C light stays on as long as the system is set to auto climate. When you use the manual adjustment, you can shut the A/C down and that seems to help.

You can also force A/C off while in auto by going to the climate screen and touching the A/C button. That way the auto still controls the fan speed and such.

[cruznroadking]

Keep in mind also that with the cold weather, it takes the engine longer to warm up & get to normal operating temperature. That's where some of your gas mileage is going.

[Vegas 400h]

Keep in mind also that with the cold weather, it takes the engine longer to warm up & get to normal operating temperature. That's where some of your gas mileage is going.

My wife has noticed that using the seat warmer also reduces mileage by about 1 mpg.

[NeoN]

My wife has noticed that using the seat warmer also reduces mileage by about 1 mpg.

is this seat warmer thing actually true? how can it cost 1mpg to run the heated seats when the engine isn't require to run them? Correct me if I'm wrong but don't the heated seats run off the auxiliary power?

[Jim Nazium]

No the seat warmer does not consume 1mpg per use. Remember, you can vary the heat setting and if anything you can use the Heat Seater to SAVE you money by improving mpg.

When cold, do not use AUTO climate, in fact keep the entire system off. Instead use the seat heater hence not requiring the engine to fire up in order to heat up the coolant for the heater core. Then when you get a chance to get up to highway speed you can reverse, turn off seat heater if you want and activate the auto climate control, since the engine is running anways it will at the same time transfer hot fluid to the heater core. Then if you are really miserly, you can after activating the auto climate control and start blowing hot air inside the passenger compartment, you can increase the temperature setting even higher and have the air divert to i.e. face and heat... THEN turn off the system alltogether, thereby the natural air that is vented into the passenger compartment will do so without using energy from the vehicle :)

Cheers,

MadloR

[NeoN]

No the seat warmer does not consume 1mpg per use. Remember, you can vary the heat setting and if anything you can use the Heat Seater to SAVE you money by improving mpg.

When cold, do not use AUTO climate, in fact keep the entire system off. Instead use the seat heater hence not requiring the engine to fire up in order to heat up the coolant for the heater core. Then when you get a chance to get up to highway speed you can reverse, turn off seat heater if you want and activate the auto climate control, since the engine is running anways it will at the same time transfer hot fluid to the heater core. Then if you are really miserly, you can after activating the auto climate control and start blowing hot air inside the passenger compartment, you can increase the temperature setting even higher and have the air divert to i.e. face and heat... THEN turn off the system alltogether, thereby the natural air that is vented into the passenger compartment will do so without using energy from the vehicle :)

Cheers,

MadloR

Thanks for the tip!!

[Jim Clark]

I don't understand how the seat heater or A/C would cause decreased mileage. Is it because the engine needs to run more to charge the batteries? Our A/C is an electric motor and not driven by the engine.

The engine needs to run more in the cold to get to, and stay at, operating temperature. It's also needed to provide heat to the cabin.

We're on our 3rd tank of gas, got 27 mpg on the first two and it hasn't been warm here recently, actually a bit cold. The car is primarily used in my wife's commute which is about 20 miles and 40 minutes. I have heard that people with very short commutes, or who typically only do short trips, have not fared as well.

She's been thrilled about using the HOV lanes on her commute, reduces drive time significantly.

[Gryphon]

I certainly don't have any empiracal data to back this up, but my gut feel is that things like seat heaters, K&N air filters, etc., are not going to have a measurable effect on fuel economy--probably more like 1/10 MPG but that's about all.

Tom

[riwyle]

If someone knows the wattage of the each seat heater, a very rough calculation could be made to determine how much energy from the fuel, and thus the amount of fuel, is needed to provide this. Lacking this, it is simply a w.a.g.

[davefordham]

I'm really new to this hybrid stuff, but I have certainly noticed in our new '08 RX400h that if you want the auto climate control to keep things warm/cool, the engine wants to be running most of the time (makes sense with coolant needing to be warm and a compressor needing to spin . . ), and if you keep both seat heaters on (or mirror defrosters, or I suppose any sizeable electrical consumer), again, the engine keeps starting. If you turn everything off though, and stay real quiet . . . . those batteries do a pretty good job! (Pretty neat car, but I still miss my old Scirocco . . .)

If someone knows the wattage of the each seat heater, a very rough calculation could be made to determine how much energy from the fuel, and thus the amount of fuel, is needed to provide this. Lacking this, it is simply a w.a.g.