Insight LOVES warm and humid

[epqsoq]

It might be my imagination, but it seems like on warm, humid days (temp over 65, dew point mid 60s or higher), the insight just wants to take off. I can park the instantaneous MPG at 75 and still be picking up speed. Drop the temperature and humidity, and I can't maintain 55 at 75 mpg on the same roads. It doesn't seem like there is enough of a difference in air density (i.e., air density is proportional to temp in degrees kelvin other factors being equal and water vapor is lighter than dry air) to account for this. Anyone else notice this or have an explanation?

[Fred]

... it seems like on warm, humid days (temp over 65, dew point mid 60s or higher), the insight just wants to take off. I can park the instantaneous MPG at 75 and still be picking up speed. Drop the temperature and humidity, and I can't maintain 55 at 75 mpg on the same roads.
... Anyone else notice this or have an explanation?

Good MPGs with the Insight on a given run, on warm to hot days have been given good coverage here at Insight Central, so yes, other Insight owners have noticed this as well. When Winter finally gets here and it cools down, then you'll see your MPGs "take a hit" over those same roads. The Winter grade gasoline also take a bite out of your MPGs so be ready for that.

Hope this helps.

Fred / Proud Owner of "The Silver Bullet"

[james]

Can't speak to humid, as we don't have that in these parts Hot days will do even better than warm, though, which is the logic behind the radiator block & hot air mods. (Do a search for details.)

[originalbadbob]

I seem to have gotten my best mileage right after a rain, and when the road is nearly dry or just enough so that the tires don't pick up any water. It would be a nice experiment to have a water drip onto the cat where I pick up my air intake to see if it makes a difference.
robert

[flunkysama]

IMHO, by far the most important aspect of weather that influences your mileage is the wind speed/direction. If you get much better mileage when it's warm and humid, that usually means a wind from the south and I'm guessing you are primarily heading north when notice MPG.
In my morning commute, I've seen 80+MPG when I have a nice tailwind. But today, with a 15MPH headwind, I only got 67MPG (and I even drove slower).

[originalbadbob]

IMHO, by far the most important aspect of weather that influences your mileage is the wind speed/direction.

I agree that wind and direction is one of the most important components, but usually in the mornings on the commute to work, there is no wind, like this morning. My usual morning commute when it's hot outside runs in the low 80s, but this morning after a decent rain, the road was damp, but not wet, and it is around 62 degrees F, which is pretty low for me to get in the 80s, but I posted an 88.6 this morning.

When it's windy and gusty, I sometimes find it difficult to get above 75 on the way home.

Rick Reece and I have had this conversation before and we both have discovered it. I usually see about 4-5% increase after a rain, providing there is no wind. My overall best mileages are hot and no wind, however.

[epqsoq]

I've been paying more attention to the wind speed/direction and it is definitely a factor. Also the prevailing winds have shifted to NW or WNW with the onset of winter, and on very windy days I'm struggling to get over 60 mpg on a commute that was averaging 70 in warm weather. Got 63.5 the other day when the winds were calm, even though the temp was only 14 degrees.

[Ian]

I wouldn't know about sultry weather, as we don't get any in and around San Francisco, but as for other uncontrollable variables I would say:

1. Wind direction and strength. In the morning it is usually still, but the ocean breeze (aka fog) kicks up on summer afternoons and my evening commute went from cross/head winds for the first 10 miles, side/cross/tail winds for the next ten, and cross/tail winds for the final 10. Typically on each 10-mile leg I would get 70, 90 and 100 mpg on a summer run that started off cool in San Francisco and ended hot on the peninsula; which brings me to . . .

2. Temperature - hotter is better, cold in an mpg killer, which includes a/c, which itself can knock off 10 mpg. Roll up the windows and as long as the temperature inside didn't fry my brain I was cool with that, even if I did have to take a cold shower when I got home.

3. Not just hills and dales, but also the road surface, the smoother (quieter) the better. This can be a 5 mpg variable. There is a section on 101 by 92 that is a magic carpet ride.

4. Rain sucks, its like wading uphill through treacle, but mercifully we don't get a whole lot of it.

I have moved and changed my commute, which is now much shorter and hillier and the traffic is more viscous and my mpg has fallen off a cliff, so maybe its time to lube up the old penny farthing . . .

[jrrs]

Originally Posted by originalbadbob

My overall best mileages are hot and no wind, however.

seconded.

i don't recall noticing any difference with humidity. am in western central NYS. usually there's not too many days close by where they're all hot but the humidity has a high variance, 'least that i recall. i'll try to keep an eye for it this summer

anyway, no wind for sure. i think of it same as the boost meter. optimally speaking i'll never touch boost or charge and have a full battery all day. i see my personal average bests in this condition. if there's a tailwind initially for you (boost), there might be a headwind in 40 minutes when you're going back home (charge) and thus the overall avg is less than if there were no wind at all.

also, there is rarely ever an optimal tailwind. it's for me frequently crosswindy, so if it is true that i'm receiving a nontrivial assist towards my desired vector, it may also be true that i'm receiving a nontrivial influence *away* from said desired vector as well. not opposite, but away even still.

*edit BBcode on quote*