Typical affect heater has on MPG?

Hi j...,

Well, yea of course the heater has an impact. Primarily, the impact is due to standing still waiting for the windows to defrost, with the engine running. The car is burning gas (denominator) while not adding to the numerator (miles driven). Secondarily, the engine wont stop when the vehicle is stationary, until the interior and engine temps are up to within a controlled range.

So, you can see, its all depends on trip length how much impact there actually is. Each defrosting is amortized over the length of the morning trip, typically. The longer the morning trip, the less the impact on overall mileage.

We who are interested in optimum mileage will run the heater just enough to see out of the windows, and wear hats and gloves to stay comfortable. This is fine when the sun is out, but it can be unpleasant on a 0 degree F morning before the sun is up, stuck in traffic.

I run my AUTO setting at 65 F, and then switch it off once up to temp, and then back on as defogging is needed. 65 is as low as the setting goes. I wish they had it setable down to like 50 F. There is no sweet spot, the higher you set it, the more gas you will use. Its that simple.

I really do not find a need for heated seats myself. Toyota was originally a weaving company, and knows fabrics well. The cloth microfiber seats in the Prius are quite warm. Leather can be bone chilling I am told.

If they really wanted to improve cold-weather comfort for drivers, with minimum mileage impact, they should add a heated steering wheel option. Then grabbing the steering wheel would keep your hands warm. Keep the head, hands and feet warm, and the rest of the body will be fine.

 

OK, here is my thought: It depends!

Assuming it is 32 degrees or lower outside.

If you are driving, say ... 30 miles, a mix of highway and city driving, (where the ICE will be off and on to provide motion) I suspect the impact is minimal. Go ahead ... turn up the heat and be comfortable.

OTOH, I sometimes let my wife out at the market door, move out in the lot and sit in the car to await her call that she is completed shopping. I press "P" and await her call. The ICE will start occassionally to maintain hot water. Obviously, that is costly (zero MPG). Short, start and stop (not stop and go traffic) driving will have the same impact.

Interestingly, under both situations .... the Volt owner will loose electric (EV) range. Several writers on the Volt thread have mentioned being cold within the vehicle. Living where it is cold 6 months of the year .... NO THANKS.

 

You house gets 0 mpg while the house heater is running. Don't use it either.

Another approach would be to figure out how much per hour it costs to keep the car warm while you are parked in it waiting for a call. It's probably 1/4 gallon per hour or less.

 

grill blocking will probably save you more than you lose turning the heat on.

 

I've noticed when at stops: I can turn the engine on/off when the ventilation system is in "Auto", by running the temperature up/down a few degrees. Tick it up, engine re-starts. Tick it down, engine shuts down again.

 

"Another approach would be to figure out how much per hour it costs to keep the car warm while you are parked in it waiting for a call. It's probably 1/4 gallon per hour or less."

This is a job for Scan Gauge II. The zero mileage engine idle trip. Works for A/C also. 0.25 gal./hr. x $3.00/gal. = $0.75 or a nickel every 4 minutes.

 

My advice to possibly reduce fuel consumption in winter:
1) leave ECO mode on (unless driving on highway or for longer trips outside of town)
2) reduce heater temperature to the lowest possible value, according to length of trip and how well dressed you are - in short trips in town, I set it to the lowest possible before reaching "LO" since I will keep my coat on - if longer, then a bit more; if a long trip on highway, then I set to 21-22C to be comfortable with no coat on since the engine is on the whole time in any case - the wind resistance will be a higher hit than the heater itself
3) as advised by others here, though I am not doing it, you can block the lower grille - there are several threads here in the forum on how to do it
4) keep the A/C system set to AUTO - it will do a good job in keeping the windows defogged - with ECO it will work to the limit and it might be that in humid cold weather the rear windows will fog slightly - use defroster/defogger as necessary

I keep in this way the fuel consumption around 5.5L/100km or less, and it doesn't shoot all the way up to 6L/100km which I never reach in winter.

 

it's like trying to score more points in a video game!

 

Boy, that is just about what I would expect from a Californian. Somewhat out of context????

 

That wasn't an airplane that went over your head.

 

I keep the temp at 67f and fan speed at 3 bars, comfortable enough for short trips. If the engine turns on while at a red light I turn off the fan.

 

65 degrees is the lowest before the 'lo' setting. I wish it went as far down as 60 degrees. That's the setting I use in my Saab in the winter and it's plenty warm.

In fact, with a coat on, 60 is almost too warm. My winter coat is intended to keep one warm down to the teens or below.

Add to that being female and 50 and well...I'm almost never cold. Haven't been in a few years now! ;-D

 

Let me check again, Lottamoxie, because I am not too sure to remember that the minimum setting is 18C/65F on my EU prius - I remember more 17C/63F - I will post again about it.

 

In the US, the lowest setting above LO is 65 F.

 

Don't think I've seen this addressed -- curious if setting the heat temperature, then turning the fans off, had the same effect as running no heat. Heat still emanates from the vents while fans are off, and at highway speeds, with temp set to, say, 80, and fans off, you get a nicely warmed cabin.

 

The European model goes down to 16C = 61F

 

Once the engine is warmed up and you are at highway speeds, any cabin heat you get is free because the engine is dumping waste heat out the radiator if you don't use it. It does take some power to run the fans but you would be hard pressed to measure the effect on fuel consumption. Running fanless is still a good thing if you are trying to squeak every foot of travel out of the gas you use.

 

Confirmed!