So yesterday I got on I-40, set cruise at 72 and reset trip A odometer. Over the relevant stretch I usually get about 51 mpg indicated (about 48-49 real) when I do this. But yesterday, I got 60 mpg indicated (about 57.5 real). I don't have an anemometer (sp?), but I did notice a real tailwind, based on how those huge flags some businesses fly were flapping. Other than that, I can't think of any reason for the improvement. Does this amount of improvement based on wind sound reasonable to the engineers here?
I have observed the same thing several times. Wind usually comes from the West down the Columbia River Gorge, with a strong headwind I might only get 35 MPG going the 200 miles to Portland. If the wind is still blowing on the return trip I might get 55 MPG or more. That is at 65 to 70 MPH, at slower speeds I don't think the difference would be as much.
That sounds reasonable to me, though I'm not the right kind of engineer to make the judgement. My fuel sucking pig Subaru, which gets 27 mpg in good summer conditions without hypermiling, and 33 mpg in the summer of 2008 with mild hypermiling, managed a 38.8 mpg tank (325 miles) on one run in large part due to strong tailwinds. Like the Prius and Civic hybrids, my Suby seems to have a sort of super highway mode, but it is normally too slow to be useful. That day's wind assist boosted that mode up to 56-60 mph on many road sections, and I was using a ScanGauge to take full advantage of it.
I used a strong tail wind to pull a 60 mpg segment from my 08 Honda Fit with automatic transmission (flat towable). Drove up the hills and glided down engine off. It normally gives me 40-42 mpg. Prius automatically kills fuel flow, so you get a similar result. Less percentage improvement since the Prius EPA number already is raised by built-in engine off Prius design.
OOOH yes, the Columbia River Gorge is a great wind tunnel for this sort of test! That and wind surfing, though I have never tried the latter.
Kgall, I travel 167 north and south during the year (80 miles RT daily) and I'm amazed at how the wind makes a difference in mpg.
I drive 50 miles each way up and down highway 75 in Oklahoma which runs 100% north/south. When we get southern winds of about 20 MPH constant, my mileage on the way home is in the low 40's. Mid 60's if it's a tailwind.
I find it helpful to think of tailwinds at highway speeds not as wind pushing from behind, but as more of a lessening of the headwind. For example, a 40 km/h tailwind while driving at 100 km/h, means you're driving 100 km/h but pushing just 60 km/h worth of wind. I scored a 3.1 L/100 km last weekend over ~100 km doing this; but was penalized 4.6 L/100 km on the return run, heading back into the wind. Yes, wind makes an immense world of difference! Nearly 300 000 km worth of travel in a 40 hp Diesel flat-backed smart has taught me this. -Iain
Had a decent tailwind 75% of the way in to work this morning... End of (28 mi) commute indicated 57.6mpg! Best I've seen so far. Hopefully it will change directions or die down before I have to head home
I pass a public park with ball fields that has flags flying on my daily commute. Whenever I see mpg above or below my normal average I always check the flags to see the wind speed and direction. A headwind and I see anywhere from a 1-5 mpg decrease and with a tailwind about the same increase. It is really nice on the drive home since I have an overall downhill drive and with a good tailwind I can really see some good 55-65 mpg stretches.
Somewhere in the Gulf region an oil baron sheik is beating his chest crying .... "65mpg- curse you Toyota!"
I ran across this thread after posting a response on this Prius C thread ... You Know You're a Prius C Owner When ... http://priuschat.com/forums/prius-c-main-forum/106679-you-know-your-prius-c-owner-when-2.html Check out one of my responses!
Thats why round trips are the best way to calculate trip mpg's. You may get 65 mpg one way and only 45 mpg the other, due to wind or elevation.
True most of the time but........ my wife has a commute that due to local weather/wind patterns gets little to no aid from a tailwind in the morning but a strong headwind on the afternoon return leg. Kinda' like folks who commute east in the mornings and west in the afternoons, the sun is always in their face.
I have this same problem. Most of the time in the early morning hours of my commute to work there is usually very little wind. In the afternoon drive home there is normally at least some amount of wind. So it very seldom cancels out between the two trips. At least my commute is east to west in the morning and back east in the afternoon so no sun in the face
The photo in my sig was taken after several hours of driving (mostly highway, some city) with a tailwind. The route is one that I take a couple times a month. Normally, I'll get 51-53mpg. So YES! A very big difference based on wind direction.
