Gas Mileage - Effect of Air Conditioning?

[seadave]

Now that summer is almost here in the Houston area, running the air conditioner is NOT optional. Any ninny from the North who thinks we can simply roll down our windows needs to try it down here when at 7:00 AM the temperature is already 80 and the humidity 95%.

It is difficult to measure how much mileage drops due to AC, but I would like to see some other guesses in addition to my own, so please post what you thing you are seeing on your Smart. With Mr. Bean, he seems to be getting 2.5 to 3.5 mpg less. I am consistently getting 36 - 38 where before my range was roughly 38 - 42. This is in the Houston suburbs, so no hills, mix of 35 - 55 roads, and about 25% doing 65 on freeways. Definitely quite a bit of sitting in traffic waiting for lights.

And your Smartie's results??

[amoore007]

I ran air all of last summer on my 110 mile commute via I59.
I say it is 4mpg lower based on 4,000 rpm or 79 mph.
It might be less if I would slow down.
I am turning 30,000 miles on the smart next week with only one service problem.
It has been a blessing during these economic times. AL

[John_H]

In the first three tanks when I didn't know the "full up" venting kicked in the A/C, I got 3-4 mpg less than the following tanks when I didn't have the A/C engaged automatically in cool weather. While I saw a "step function" in mpg, the break-in of the car may have affected the results slightly. I tend to run my tank down to around 0.1g before fillup so the results I get for a tank are pretty accurate.

I have at least 20 miles below 0.0g but a recent check of how much fuel under 0.1g by weight suggests that might be about my limit!

[chieftmc]

Originally Posted by John_H

In the first three tanks when I didn't know the "full up" venting kicked in the A/C, I got 3-4 mpg less than the following tanks when I didn't have the A/C engaged automatically in cool weather. While I saw a "step function" in mpg, the break-in of the car may have affected the results slightly. I tend to run my tank down to around 0.1g before fillup so the results I get for a tank are pretty accurate.

I have at least 20 miles below 0.0g but a recent check of how much fuel under 0.1g by weight suggests that might be about my limit!

John,

You may want to peruse this:Pro-Tech Auto Center-Fuel Pumps

[seadave]

Originally Posted by John_H

In the first three tanks when I didn't know the "full up" venting kicked in the A/C, I got 3-4 mpg less than the following tanks when I didn't have the A/C engaged automatically in cool weather. While I saw a "step function" in mpg, the break-in of the car may have affected the results slightly. I tend to run my tank down to around 0.1g before fillup so the results I get for a tank are pretty accurate.

I have at least 20 miles below 0.0g but a recent check of how much fuel under 0.1g by weight suggests that might be about my limit!

OK - what the heck is "full up" venting and A/C engaging automatically??

[John_H]

Your vent dial has 12 settings with three points of 100% of the air one direction: at 4 o'clock the air is 100% out of the console vents, at 8 o'clock the air is 100% out of the floor vents, at 12 o'clock the air is 100% out of the windshield vents. It's the 12 o'clock position I call "full up" venting because SO many people talk about the 12 o'clock position being the "defrost" setting which doesn't describe the reason I want to blow air there.

When the vent is turned to all-windshield at the 12 o'clock position, the A/C is automatically engaged even though the A/C button has not been pressed nor is there indication the A/C is on from the LED on the button.

So. If your vent dial is set to 12 o'clock or "full up" your A/C is on unless the outside temperature is approaching freezing.

[CWCjr]

Originally Posted by chieftmc

John,

You may want to peruse this:Pro-Tech Auto Center-Fuel Pumps

Do you or anyone else know if the Smart Car's fuel pump is in the gas tank?

[Old smart]

Originally Posted by CWCjr

Do you or anyone else know if the Smart Car's fuel pump is in the gas tank?

Yes, it is. The smart fuel pump shuts itself off before it runs dry and overheats or pumps air into the supply line.

[forestacademy]

In the smart guide to Maximizing Fuel Economy
http://static.ning.com/smarturbanist...%20Economy.pdf

It clearly stated if you run the AC in stop and go traffic it will increase consumption by up to 30%, But at steady Highway speeds the A/C barely increases fuel consumption.

And - Close your windows when driving on the highway. Open windows increase the aerodynamic load thereby making your engine work harder.

So smarts answer is open windows in stop and go trafic with a/c off, and close them at highway speeds with A/C on.
So avoid stop and go traffic in the hot weather.

[seadave]

Originally Posted by forestacademy

In the smart guide to Maximizing Fuel Economy
http://static.ning.com/smarturbanist...%20Economy.pdf

It clearly stated if you run the AC in stop and go traffic it will increase consumption by up to 30%, But at steady Highway speeds the A/C barely increases fuel consumption.

And - Close your windows when driving on the highway. Open windows increase the aerodynamic load thereby making your engine work harder.

So smarts answer is open windows in stop and go trafic with a/c off, and close them at highway speeds with A/C on.
So avoid stop and go traffic in the hot weather.

OK, so it's cool enough in Wisconsin so you can turn the ac off and open the windows in stop and go traffic. In Houston such an action would typically leave you in a puddle of sweat in about five minutes. The car would also have to be fitted with some sort of bilge pump in the floorboard to remove the accumulation of sweat before it starts sloshing around. If you had a passenger they would likely file suit for unusual and cruel punishment.

The folks at Smart as well as my friends in cooler climes will have to read my lips - RUNNING WITHOUT A/C IN HOUSTON SUMMERS IS NOT AN OPTION. ...But considering the amount of fuel consumed, I'll keep 'er running, thank you very much. Also interesting they say up to 30%. So far the replies on this post have pegged it more like 10-15%.

Thanks for the good comments!

keeping cool in houston,

seadave