Skeptic Friends Network

Username:
Password:
Save Password
Forgot your Password?
Home | Forums | Active Topics | Active Polls | Register | FAQ | Contact Us  
  Connect: Chat | SFN Messenger | Buddy List | Members
Personalize: Profile | My Page | Forum Bookmarks  
 All Forums
 Our Skeptic Forums
 General Skepticism
 Hypermiling
 New Topic  Reply to Topic
 Printer Friendly Bookmark this Topic BookMark Topic
Previous Page | Next Page
Author Previous Topic Topic Next Topic
Page: of 3

Dave W.
Info Junkie

USA
26009 Posts

Posted - 06/30/2008 :  20:37:05   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
This evening, I finally got a chance to clean out my car (including putting the doughnut spare back properly after using it last fall). I didn't make any of the more serious modifications I was talking about before, but I still got rid of maybe 30 or 40 pounds of accumulated debris and winter tools that I don't need in Summer (the ice scrapers and a shovel). I even took the coins out of the center console that have sat there, unused, for many, many years. So if the stats I read earlier are correct, I just added maybe 0.2 MPG. Except that I cleaned it out to make room for the hundred pounds of boxes of stuff that I need to transport tomorrow morning. Well, that will be one trip, while the cleanliness will be less temporary.

I bet I could vacuum out another five pounds of dust and crap, if I could find the time to vacuum my car...

Last Saturday, I went to Baltimore. Not having been to the place I was going, I was at TomTom's mercy. TomTom first offered me a route with tolls, but being pressed for time and having only five bucks, I opted out. Big mistake from a Hypermiling point-of-view, since the alternative TomTom gave me had me going straight through the middle of a large urban area. Stoplights every block, in other words. And the temperature gauge creeped high enough that I wound up driving through downtown Baltimore in the Summer temps with the heat on full-blast to help cool the engine. And going back (through the middle of town, again), I was in the middle of a thunderstorm on streets I'd never driven before (a nightmare, to put it simply). The trip, each way, was nearly as long as my round-trip daily commute.

However, I just gassed up again this evening, and learned that this little foray of horrors only cost me about one MPG.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

Cuneiformist
The Imperfectionist

USA
4954 Posts

Posted - 06/30/2008 :  20:41:26   [Permalink]  Show Profile Send Cuneiformist a Private Message  Reply with Quote
Dave! I lived in B'more for 8 years! You should have asked and I'd have helped with the best route to wherever you were going. Unless you were going for some of the city's more infamous destinations (which I of course doubt), and then I know nothing...
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 06/30/2008 :  20:57:30   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Believe me, Cune, I would have asked had I thought about it before I got in the car. TomTom's route wouldn't have been so bad if it had been Spring or Fall. The toll route was, if I recall correctly, one minute shorter but four miles longer than the non-toll route, so it wasn't all highway.

Had I gone some other way, though, I would have missed out on this wonderful scene: I was driving along for a couple miles with a Baltimore cop behind me. I happened to notice up ahead that there was an SUV parked out in front of a corner liquor store (somewhere in the middle of town). I was getting close to the SUV when the SUV's driver's door opens up (which made me move left somewhat) and the woman in the driver's seat leans out and vomits onto the street. Needless to say, the cop's lights went on almost instantly, and I found myself without an escort any longer.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

Hawks
SFN Regular

Canada
1383 Posts

Posted - 07/01/2008 :  20:07:55   [Permalink]  Show Profile  Visit Hawks's Homepage Send Hawks a Private Message  Reply with Quote
Originally posted by Dave W.
So, Cune, you haven't gone hard-core by turning the engine off while coasting?

I did something like that by mistake the other week. The ignition in our Dodge Grand Caravan sits quite close to my knee and I have, a few times, managed to switch the car off while simply moving around a bit. 2-3 times this has happened while reversing in parking lots - not a huge problem. Last time I was doing 90 km/h. The engine died, as did the power steering. That was scary - and something to remember if you try something like that on purpose.

METHINKS IT IS LIKE A WEASEL
It's a small, off-duty czechoslovakian traffic warden!
Go to Top of Page

Dr. Mabuse
Septic Fiend

Sweden
9677 Posts

Posted - 07/02/2008 :  07:03:28   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
I also had a scare once, just because in a lapse of thinking, I lost power steering and power breaks that I needed after I had turned the engine off, on purpose. Fortunately, I was just coasting with the clutch with gear in place, so I only had to pop the clutch to get back control.

I also had an episode when I was driving on one of the larger roads between Gothenburg and Stockholm, and ran out of gas. I was doing about 100km/h when that happened, and coasted several hundred meters on a dead engine to finally turn off the road to a gas station. I just had enough momentum to carry me there and only used the breaks a little at the end as I was doing perhaps 10km/h before I had to stop.
In order to get to the station I had to do a left turn, but it was late evening, and traffic was low so got lucky...

Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder.
Go to Top of Page

moakley
SFN Regular

USA
1886 Posts

Posted - 07/02/2008 :  16:33:07   [Permalink]  Show Profile Send moakley a Private Message  Reply with Quote
Reviewing the list I found only a handful of things that I'm aware that I do.

I drive a 2006 Honda Accord manual shift. Each week I make the trip from Charlotte, NC to Columbia, SC twice. So over 90 percent of the miles I drive are on the interstate. For the first 18 months owning the car I was getting just over 34 mpg. During the past month I have slowed down by 5 miles per hour and am now getting just over 37 mpg. It was difficult to slow down initially, but if this increase in mpg continues I believe I could get use to it.

Also, I have noticed, on this same stretch of interstate, during the past couple of months that semis rarely travel above 70. And that most cars and trucks have slowed down. Some have taken it to an extreme though traveling at between 55 and 60 mph. Now that's just a little too slow and I believe dangerous.

Life is good

Philosophy is questions that may never be answered. Religion is answers that may never be questioned. -Anonymous
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 05/22/2009 :  21:31:48   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Last Wednesday, I fueled up. Exactly one year after starting to keep records of my fill-up mileage. And the most-noticeable thing about the data is the seasonal change.

The winter was hard on my mileage. The summer was hard, also, due to air-conditioner use. Spring and fall give me the best numbers. And it wasn't as if I spent the winter slogging through snow, we had very little precipitation. It was just the cold air that capped my mileage.

After throwing out the highest and lowest figures (due to pump screw-ups, both times), my annual milage average was 34.41 mpg, with a high of 37.01 mpg last September, and a low of 31.8 mpg last December. December through March, my average was about 32.5 mpg. September and October of last year saw an average of about 36.2 mpg. And my mileage has been steadily climbing so far this Spring.

So basically, pleasant weather does more for my mileage than I can.

And now that I've seen a whole year of data, I'm going to stop collecting it. I'll save a few fractions of a tree, and have a few more seconds every week to spend on other pursuits. I'll probably keep reseting the trip odometer with every fill-up, just to make sure things don't go horribly awry without me noticing, but I really didn't need to know that I went 17,853.7 miles on 518.8 gallons of fuel in the last year.

Oh, if you're interested in hypermiling more for the monetary savings at the pump than for the greening of the planet, the best thing I did for that in the last year was to get a gas credit card which gives me a 5% rebate at the station I've used for years. Dollar-wise, it's the equivalent (for me) of getting an extra 1.6 mpg. I don't know how many other oil companies offer such a deal, but I get my gas from Shell (and their pump prices have generally been within a penny or two of the Exxon station right across the street).

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

Cuneiformist
The Imperfectionist

USA
4954 Posts

Posted - 05/24/2009 :  16:56:39   [Permalink]  Show Profile Send Cuneiformist a Private Message  Reply with Quote
Actually, Dave, this became apparent to me after 3 Ithaca winters-- much more so than in Baltimore, but I am sure that my record-keeping wasn't as good as yours. In any event, I noticed that my mileage dropped quite a bit in the winter. In part, this had to have been due to the warm-up-the-car-for-5-minutes thing I'd do when the temps were in the 20° range. I also imagine that the cold didn't help my tire pressure much. I know they change the gasoline formula, too. I wonder if that plays a part...
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 05/24/2009 :  19:52:10   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by Cuneiformist

Actually, Dave, this became apparent to me after 3 Ithaca winters-- much more so than in Baltimore, but I am sure that my record-keeping wasn't as good as yours. In any event, I noticed that my mileage dropped quite a bit in the winter. In part, this had to have been due to the warm-up-the-car-for-5-minutes thing I'd do when the temps were in the 20° range. I also imagine that the cold didn't help my tire pressure much. I know they change the gasoline formula, too. I wonder if that plays a part...
And here I was, thinking about air density changes.

There's a hill I go down on my way home from work. In warm weather, in drive, foot off the gas, I can pick up a few miles-per-hour going down that hill. Below 50 degrees F or so, though, my speed stays more-or-less constant down that hill (hard to tell with the stock spedometer). Since the hill is far enough from work that the engine, drivetrain and tires will all be up to operating temperatures, the only differences will be air density. Outside, dragging on the car body and (thanks to you) inside the tires.

Actually, I think it might be the case that the tire air is going to get to about the same temperature, regardless of the outside air temps, because rubber isn't that great at transferring temperatures. In other words, cold tires will definitely have a lower air pressure in winter than in summer, but what about tires that have been driven at 35 or 45 for about six miles?

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 05/24/2009 :  20:03:10   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by Cuneiformist

...the warm-up-the-car-for-5-minutes thing I'd do when the temps were in the 20° range.
Forgot about the above. One thing the real hypermilers are adamant about: if driving a cold engine is going to damage yours, then you need to get it repaired rather than wait every morning for it to warm up.

Get in the car, buckle up, put it in neutral, foot on brake, release parking brake, start the car, put it in drive (or reverse) and go!

Of course, that's the sequence I've had the most problems with (it's so "natural" to turn the key right after putting it in the ignition). That and turning the car off first when parking.

On the other hand, even though my recent change in work schedule gets me to the office when there's tons of up-front parking, I'm still parking way in the back, to avoid burning pointless cross-the-parking-lot gasoline. Parking up close would save me, at most, 30 seconds of walking anyway.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

R.Wreck
SFN Regular

USA
1191 Posts

Posted - 05/24/2009 :  20:37:55   [Permalink]  Show Profile Send R.Wreck a Private Message  Reply with Quote
Originally posted by Dave W.

Originally posted by Cuneiformist

Actually, Dave, this became apparent to me after 3 Ithaca winters-- much more so than in Baltimore, but I am sure that my record-keeping wasn't as good as yours. In any event, I noticed that my mileage dropped quite a bit in the winter. In part, this had to have been due to the warm-up-the-car-for-5-minutes thing I'd do when the temps were in the 20° range. I also imagine that the cold didn't help my tire pressure much. I know they change the gasoline formula, too. I wonder if that plays a part...
And here I was, thinking about air density changes.

There's a hill I go down on my way home from work. In warm weather, in drive, foot off the gas, I can pick up a few miles-per-hour going down that hill. Below 50 degrees F or so, though, my speed stays more-or-less constant down that hill (hard to tell with the stock spedometer). Since the hill is far enough from work that the engine, drivetrain and tires will all be up to operating temperatures, the only differences will be air density. Outside, dragging on the car body and (thanks to you) inside the tires.

Actually, I think it might be the case that the tire air is going to get to about the same temperature, regardless of the outside air temps, because rubber isn't that great at transferring temperatures. In other words, cold tires will definitely have a lower air pressure in winter than in summer, but what about tires that have been driven at 35 or 45 for about six miles?


According to Tirerack:

A vehicle's fuel economy is the direct result of its total resistance to movement. This includes overcoming inertia (Newton's Law), driveline friction, road grades, tire rolling resistance and air drag. In order to offer the same level of performance, heavy vehicles require more power (and more fuel) than light vehicles. All-wheel and four-wheel drive vehicles require more power than two-wheel drive vehicles and boxy vehicles require more power than low drag aerodynamic vehicles.

But how much influence does each of these elements have and when are their influences felt? Once you eliminate the fuel converted into heat by the engine, the relative percent of influence that these other factors represent during stop-and-go city driving are very different then during steady-speed, highway driving.

During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%.

Overcoming inertia no longer plays an appreciable role in the vehicle's resistance during steady speed highway driving. For those conditions it is estimated that driveline friction is about 15%; air drag is about 60% and tire rolling resistance represent about 25%.


So it depends on your driving conditions.

As far as tire air pressure in winter goes:

The rule of thumb is for every 10 Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower).

...

Next we evaluated the affects of heat generated by the tire's flexing during use. We tried to eliminate the variable conditions we might encounter on the road by conducting this test using our "competition tire heat cycling service" that rolls the tires under load against the machine's rollers to simulate real world driving. We monitored the changes in tire pressure in 5-minute intervals. The test tires were inflated to 15 psi, 20 psi, 25 psi and 30 psi. Running them all under the same load, the air pressure in all of the tires went up about 1 psi during every 5 minutes of use for the first 20 minutes of operation. Then the air pressures stabilized, typically gaining no more than 1 psi of additional pressure during the next 20 minutes.


So your tire pressure will increase about 4 to 5 psi maximum from driving, which will offset a temperature change of about 40 to 50F. In your case (six miles at 35 to 45 mph, you'd get about 2 psi increase, or enough to offset a 20F change in ambient temperature.

Summer blend gas may give you slightly better mileage (source).

Don't forget about the increased efficiency from a colder heat sink as shown by the Carnot efficiency. Although you will never attain the Carnot value, all other things being equal, your engine is more efficient in winter than summer.


The foundation of morality is to . . . give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibliities of knowledge.
T. H. Huxley

The Cattle Prod of Enlightened Compassion
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 05/24/2009 :  21:10:57   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by R.Wreck

According to Tirerack:
...air drag is about 60%...
I figured it'd be highest.
So your tire pressure will increase about 4 to 5 psi maximum from driving, which will offset a temperature change of about 40 to 50F. In your case (six miles at 35 to 45 mph, you'd get about 2 psi increase, or enough to offset a 20F change in ambient temperature.
Actually, because the pressure increases with time regardless of cold pressure, the summer/winter difference will always be based on air temperature at the same point in my drive home. So the difference between a 40-degree day and an 80-degree day will always be 4 psi. Now, if my cold tires are 28 psi in summer, they'll be 30 psi by the time I get to the hill. My cold tires in winter will be 24 psi, and get up to 26 psi at the hill. What is the difference in rolling resistance between those two psi values (all else being equal) that goes into the 25% effect that tire pressure is estimated to have on my car's total resistance to movement?

And is it that difference, or the increased air drag, which has more of an effect on my downhill coasting performance? (I know it will be some of both, but which is larger?)
Don't forget about the increased efficiency from a colder heat sink as shown by the Carnot efficiency. Although you will never attain the Carnot value, all other things being equal, your engine is more efficient in winter than summer.
Yeah, except that the opposite is reflected in real-world gas mileage. If you want high mileage, don't drive in the cold.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page

Dr. Mabuse
Septic Fiend

Sweden
9677 Posts

Posted - 05/24/2009 :  21:59:52   [Permalink]  Show Profile  Send Dr. Mabuse an ICQ Message Send Dr. Mabuse a Private Message  Reply with Quote
When the engine is cold, it's running on a rich mixture. Both at startup and the first minute or few. This to shorten the warmup period of the engine, and ensure drivability.
Not until the lambda sensor reaches operating temerature does the ECU (engine control unit) start regulate lambda for optimal air-fuel mix.

Also, if you floor the pedal, at some point the ECU starts enriching the mix for cooling purposes. This differs from each car and engine model. But usually above 70-80% throttle and above 2500-3000rpm, though in some flexi-fuel engines it doesn't happen at all, and other models the enriching starts at 1500rpm.
The purpose is to avoid overheating the valves.

Dr. Mabuse - "When the going gets tough, the tough get Duct-tape..."
Dr. Mabuse whisper.mp3

"Equivocation is not just a job, for a creationist it's a way of life..." Dr. Mabuse

Support American Troops in Iraq:
Send them unarmed civilians for target practice..
Collateralmurder.
Go to Top of Page

astropin
SFN Regular

USA
970 Posts

Posted - 05/26/2009 :  18:33:57   [Permalink]  Show Profile Send astropin a Private Message  Reply with Quote
I feel guilty even being in here.

I drive a 2007 Dodge Charger R/T with the "Road and Track" package.

On the plus side (if there is one) it does shut down to only four cylinders when I'm cruising....even at highway speeds. But it's still a pig of a car with a big engine. I have to admit that it is fun to drive though.

I can eek out 30mpg cruising at 50-60mph. But hit the accelerator and she dives into single digits. My overall is right around 19-20.....not very good.

Unfortunately my other vehicle is even worse.....need something to haul the boat and a 4x4 is virtually a must in the winters where I live.

I would rather face a cold reality than delude myself with comforting fantasies.

You are free to believe what you want to believe and I am free to ridicule you for it.

Atheism:
The result of an unbiased and rational search for the truth.

Infinitus est numerus stultorum
Go to Top of Page

Dave W.
Info Junkie

USA
26009 Posts

Posted - 05/26/2009 :  19:09:58   [Permalink]  Show Profile  Visit Dave W.'s Homepage Send Dave W. a Private Message  Reply with Quote
Originally posted by astropin

I feel guilty even being in here.
Don't. The real point is that by changing your driving habits, you can get better mileage with whatever vehicle you drive (or tow a boat). If I remember correctly, there are some tips specifically for 4x4 drivers. Why get 8 mpg when you could be getting 8.5 mpg in a vehicle you need to drive?

Besides, as I said in the OP, I'm not doing everything I could do to get better mileage. For example, the money saved by driving the limit isn't worth (to me) the extra time my commute would take. We're talking about hypermiling as a choice, not as a duty.

It is okay to not drive a little tiny car that gets 1,000 mpg. At least, it's okay now. When they make a little tiny 4x4 that gets 1,000 mpg and can tow a boat, then I would hope you'd switch.

- Dave W. (Private Msg, EMail)
Evidently, I rock!
Why not question something for a change?
Visit Dave's Psoriasis Info, too.
Go to Top of Page
Page: of 3 Previous Topic Topic Next Topic  
Previous Page | Next Page
 New Topic  Reply to Topic
 Printer Friendly Bookmark this Topic BookMark Topic
Jump To:

The mission of the Skeptic Friends Network is to promote skepticism, critical thinking, science and logic as the best methods for evaluating all claims of fact, and we invite active participation by our members to create a skeptical community with a wide variety of viewpoints and expertise.


Home | Skeptic Forums | Skeptic Summary | The Kil Report | Creation/Evolution | Rationally Speaking | Skeptillaneous | About Skepticism | Fan Mail | Claims List | Calendar & Events | Skeptic Links | Book Reviews | Gift Shop | SFN on Facebook | Staff | Contact Us

Skeptic Friends Network
© 2008 Skeptic Friends Network Go To Top Of Page
This page was generated in 0.38 seconds.
Powered by @tomic Studio
Snitz Forums 2000