First of all, condolences to your friend. Next, glad to hear your smart performed expectedly well on your long trip.
Regarding the A/C, I have a big concern about your well-intended methodology. The reason for my concern is the wind factor while traveling north vs. south. I put 30K miles on a Honda Insight traveling between San Diego and Los Angeles (110 miles each direction), and I routinely monitored my mileage extremely precisely. Often I did the 'run' in both directions with no lag time before making the return. I kept all variables as consistent as possible to try to isolate causal factors that might affect mileage. The Insight has a very low coefficient of drag, so its penalty due to wind should be minor compared to many other cars. However, even under light wind conditions, while keeping the A/C constant in both directions, maintaining equivalent speeds, etc., my NORTHBOUND mileage always exceeded my SOUTHBOUND mileage by 4-10 MPG. (Overall freeway fuel economy would range from 60 to 85 MPG.)
I would not be at all surprised if your mileage variation were due primarily to your direction of travel. With the large frontal area of the smart and not-great coefficient of drag, the freeway penalty running against the wind could account for the difference you experienced.
With that said, I'd love to hear from a ScanGauge user who could make the SAME run in the SAME direction under the SAME traffic, speed, weather, and hill conditions... and see what effect A/C usage has on fuel economy.
Thanks for the report, and many more smart miles to you!
Steven,
You could be correct, there are lots of variables that could come into play. Would have been nice to have a scan guage to better see what was happenning. I don't think the wind was too much of a factor as it was light and from the east while my route was North/South.
It's also true that I gained some slight elevation going North and benefited by a slight elevation decline heading south. While the elevation changes are not great they may have had something to do with the differences.
Just wanted to report my experience. Appreciate the comments and suggestions as well as the condolences from all.
a 6-7 mpg differential is what I'm getting between a/c on and off using my scanguage as an indicator as well as what it shows at the pump... avg 37mpg vs 42mpg in mostly city driving, with 25% stop/go traffic
I expect AC to effect mpgs some depending on the circumstances, but hey you don't want to cook in the car and opening the windows will increase gas consumption at speed even more so what are you gonna do It is another reason tint is beneficial though, by cutting the UV it does help cut down the heat
Oh, here's a little blurb I ran across that might be handy, not sure if it is really universally applicable though:
"According to AAA, the magic number is 40. So, if you are driving over 40 miles per hour, use your car's air conditioning. If you are driving under that, you'll use less gas if you open the windows to cool down. What you do if you're cruising at a steady 40 mph is up to you."
The weather was hot sunny and humid with temps in the high 80s both ways.
My speed on the trip in both directions averaged between 65 and 77 MPH.
One possibility (and this happens to many of us) - is that you might have been in more hurried on your trip up, and hence averaged more in the 70's then on the way back home?
That would certainly cut into your mpgs as well.
One possibility (and this happens to many of us) - is that you might have been in more hurried on your trip up, and hence averaged more in the 70's then on the way back home?
That would certainly cut into your mpgs as well.
Appreciate the comment. While I didn't try to make this test scientific, not even deciding to do it until I saw what my MPG were on the Northbound trip my travel time going and coming was almost identical at 8 Hours and 15 minutes with the same number of stops although the length of the stops likely varied slightly.
Sorry about the loss.
Great test. I'm wondering if you used recirculate mode or was using 100% outside air?
I think recirculation mode can help reduce the amount of time the A/C pump runs and reduce consuption.
I use this on other cars to get maximum economy, once in a while switch to outside air for a few minutes if the air starts to smell bad.;)
Sorry about the loss.
Great test. I'm wondering if you used recirculate mode or was using 100% outside air?
I think recirculation mode can help reduce the amount of time the A/C pump runs and reduce consuption.
I use this on other cars to get maximum economy, once in a while switch to outside air for a few minutes if the air starts to smell bad.;)
I was using thr recirculate mode primarily due to the very high humidity.
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It is another reason tint is beneficial though, by cutting the UV it does help cut down the heat
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