Interesting observation in Central Florida....

[Aviation Pro]

...as I drove to the beach in my 2003 Saturn Ion this weekend (avg. MPG in city/hwy - 29/39), I noticed that nearly all the SUCKVs were driving about 10 miles slower than the posted speed limit. Now I hate to burst their stupid gas hog bubble but they should have studied harder in high school then they would have known that f=ma and would have figured out that they still have to move all that mass.

Bottom line for better gas mileage, buy a light car.

[Warpy]

1. However, they are doing some homework

and that homework is telling them that going slower does give them a lot better mileage in those hogs.

People are still driving those things because they can't sell them for enough to pay off the loan. The smart ones are slowing down to save gas.

The stoopid ones are the ones who are doing 95, thinking if the car is running for 2 minutes less time, they're saving gas.

[MercutioATC]

2. Same here in Ohio...and it's annoying.

The least they could do is confine their "energy savings" to the right lane on multi-lane roads.

[Fumesucker]

3. The bigger SUV's don't necessarily save gas by slowing down..

A family member of mine has a 97 Expedition with the SOHC 4.6, a towing package and a real time MPG readout..

Best gas mileage is between 55 and 65 mph @ 22 mpg..

At 44 mph the lockup overdrive falls back into the next lowest gear, the torque converter unlocks and efficiency plummets.. Literally 17 mpg @ 35 mph.

Yes, I know it's counterintuitive and all but a lot of cars are designed for maximum economy around 60 to 65 mph and driving slower or faster than that puts them in an uneconomical portion of the engine Brake Specific Fuel Consumption map (BSFC).

http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

Below is a BSFC map for a Prius.. Note that at some loads and RPM's the fuel efficiency is more than double that at others (230 g/KWh versus 500 g/KWh). It's also worth noting that the best efficiency is gained when the engine is at or near full load at medium RPM's (throttle wide open, in other words).

There are ways to get around this problem and increase fuel efficiency markedly at low speed but they do not involve just putting the vehicle in drive and then driving slowly and gently.

[nono]

4. Gas Mileage

Took a short trip (70 mi.) on my scooter today, passed a few slower ones on I-10. My speed was about 70mph and I burned a little over 1 gal of gas.

[Aviation Pro]

5. Basic physics....

...if you're light you go farther using an equivalent amount of PE than if you're heavy. (PE in this case is chemical energy which eventually converts to mechanical energy).

[hokies4ever]

14. Are you cramming for your physics exam?

:rofl:

[Aviation Pro]

25. Been there, done that....

...I use this stuff everyday.

[Marrah_G]

9. I would love to be able to get by on a scooter or motorcycle

Unfortunately until the kid leave home that's not going to be able to happen.

[Aviation Pro]

26. I have a very light car that fits the bill....

...again, we need to change the way we think.

[Marrah_G]

34. I would love to be in a postion to buy something different.

Right now I literally live paycheck to paycheck as a single working class mom. There is not way for me to change vehicles for at least another year and a half. Even then it sketchy.

I have changed the way I think. I've changed the way we live. Unfortunately many of the things I would like to change are road-blocked due to finances.

I'm growing a veggie garden, hanging clothes out, shopping on the way home from work, using coupons and shopping sales.

Unfortunately all that won't be enough when winter hits and heat costs 1000 dollars a month during the cold spells.

I'll figure it out somehow.

[Aviation Pro]

36. When you do, go with a used Ion....

...great gas mileage, simple, low maintenance costs. I earn a pretty decent salary, but I live far below my means and the car is just right.

[Marrah_G]

44. I will definitely remember that

Until then the 2000 minivan will have to do. Fortunately the only repairs I've had to make are tires.

[hokies4ever]

Whenever things are tough just remember

that what doesn't kill us makes us stronger. I view our life experiences kind of like a woven tapestry. Sometimes it's tempting to wish away certain 'bad' things in life. But who is to say that if we pull one thread out, the whole tapestry won't fall apart?

[nadinbrzezinski]

28. May I suggest a light car that is a hybrid

[Marrah_G]

33. A new car is not in the budget

I have a year and a half left to pay on this. Maybe then I can look into trading for something more gas friendly. Right now I literally live paycheck to paycheck.

[nadinbrzezinski]

47. I fully understand

[aquart]

6. We told them not to buy the damn things.

They sneered at us.

[Aviation Pro]

7. Of course, stupid people always sneer....

...at common sense. One of the memes passed around during the rush to buy the biggest, baddest SUCKV around was that it will keep you 'safer' because of all the steel that surrounds you. Surprise to the morons, no it doesn't, all that mass (PE) x acceleration turns into a kinectic energy force that mashes the stupid he-men and soccer moms into mushy balls of goo when the inevitable accident happens.

Get better at driving and you won't have an accident. Also, I'm quite sure that there are plenty of data that support that a lot of SUCKV drivers are legally drunk when they crash.

[hokies4ever]

12. Gas mileage not the same at all driving speeds

Even in airplanes:
http://abclocal.go.com/wabc/story?section=news/local&id=6117012
"Airlines slow down for gas mileage"

[malaise]

8. Funny isn't it

I have no sympathy for people who bought SUVs.

[Vickers]

10. Where did you get those mileage estimates for the Ion?

That highway number seems a bit high (by 10 or so).

FTR, I was driving back from Georgia on I-95 yesterday all the way to Palm Beach County, and the SUVs and trucks for the most part were whipping right along (80 - 85). Some people never learn.

I did notice that there seemed to be fewer semis, and the ones that were out were going pretty slow.

[Aviation Pro]

27. Personal experience....

...I used to drive 240 miles one way, two days per month. I simply filled the car (13.3 gallons), drove between 60 - 65 MPH, and recorded the start and stop trip distance. Generally, it took between 6.1 and 6.4 gallons (6.4 if I drove at 65, 6.1, surprisingly, at 62). Averaging the trips I was able to squeeze 39 MPG out of the car. Of course, I keep the vehicle well maintained and in Florida at sea level on flat roads I have less need for power than in a hilly or mountainous area, but the numbers are what they are.

As far as city driving, I fill up on average every 11 - 12 days. Again, I know the distance I've traveled and just did the math at that point. Fortunately, I don't have to drive that much.

All this will change when I move out to Colorado later this year, but fortunately, I will only be six miles from work, which will probably extend my fill time to 14 - 15 days. (Even at $5.00/gallon it will still be manageable - $130/month).

[hokies4ever]

11. You're wrong, and here's why

You're assuming that gas mileage is the same at all speeds. The engine is not equally efficient at all speeds.

[Aviation Pro]

29. I know that, but you still have to move the weight....

...and unless you want to get into a physics and math fight over torque and forces affecting gas mileage I suggest you just use a 10% variance for the SUCKVs at any speed (oh, by the way, most stupid SUCKV owners trail stuff - like gas sucking boats. What happens to their efficiency then?).

[hokies4ever]

35. Your force balance is faulty

why do you mention potential/kinetic energy but not the forces actually involved in a force balance on the car?

[Aviation Pro]

39. Because I don't do automotive physics....

...wanna talk airplanes? I'll be happy to.

[hokies4ever]

42. Force balances can be done on any object

You might want to study harder on that physics final before you show up to take it tomorrow. :rofl:

Anyway, I thought we were talking about cars on the road? The same principles apply to airplanes as well. I linked to an article in another one of my posts on this thread concerning airlines slowing their planes down to save fuel. The analogy is applicable to cars as well.

[Aviation Pro]

48. That's a cost index break point....

...and there's a lot more involved than just slowing down an airplane to a predetermined N1 (stage/compressor speed) and a corresponding Mach number (usually .72). Reduced thrust takeoffs, taxiing with one engine and using jet stream dynamics are just some of the ways that airlines save money on fuel.

Want to know how airlines also reduce fuel burn? They take weight off the aircraft. Therefore, instead of having 10 cases of Coca-Cola on board, they reduce it to 3. Have you noticed that you never get a full can of Coke anymore? There's the reason.

Yes, balance of forces is a critical component of determining the efficacy of flight. For us pilots we use four forces (lift, weight, thrust, drag). The engineers use three because that's how they're trained.

[hokies4ever]

49. Really? Less weight = less fuel consumption?

Next you'll be telling me that the earth is round. :rofl:

[hokies4ever]

13. More details of why you're wrong

http://finance.yahoo.com/family-home/article/104752/Slow-Down-a-Lttle-Save-a-Lot-of-Gas

"In a typical family sedan, every 10 miles per hour you drive over 60 is like the price of gasoline going up about 54 cents a gallon. That figure will be even higher for less fuel-efficient vehicles that go fewer miles on a gallon to start with.

The reason is as clear as the air around you.
When cruising on the highway, your car will be in its highest gear with the engine humming along at relatively low rpm's. All your car needs to do is maintain its speed by overcoming the combined friction of its own moving parts, the tires on the road surface and, most of all, the air flowing around, over and under it.

Pushing air around actually takes up about 40% of a car's energy at highway speeds, according to Roger Clark, a fuel economy engineer for General Motors.
Traveling faster makes the job even harder. More air builds up in front of the vehicle, and the low pressure "hole" trailing behind gets bigger, too. Together, these create an increasing suction that tends to pull back harder and harder the faster you drive. The increase is actually exponential, meaning wind resistance rises much more steeply between 70 and 80 mph than it does between 50 and 60.

Every 10 mph faster reduces fuel economy by about 4 mpg, a figure that remains fairly constant regardless of vehicle size, Clark said. (It might seem that a larger vehicle, with more aerodynamic drag, would see more of an impact. But larger vehicles also tend to have larger, more powerful engines that can more easily cope with the added load.)"

[Fumesucker]

15. The article you quote is very simplistic

And ignores a lot of intricacies of automobile design.

As I pointed out in my post above, engines are not uniformly efficient under all RPM and load regimes, in fact the efficiency can vary by 100% or more.

[hokies4ever]

16. If the engines are not uniformly efficient under all RPM and load regimes

then why would you expect gas mileage to be the same at all speeds?

[Fumesucker]

17. Where did I say that? n/t

[hokies4ever]

19. "engines are not uniformly efficient under all RPM and load regimes"

in the post I responded to

Just admit that you're wrong and we can agree. :rofl:

[Fumesucker]

21. No..

The part about "then why would you expect gas mileage to be the same at all speeds?"

Where did I say that?

[hokies4ever]

23. That was my question to you

You state that an engine changes efficiency at different "RPM and load regimes".

Is the RPMs in an engine constant at different speeds? Keep in mind that many cars have a dial for this. It's the one that goes from low to high and then back to low again when gears change.

[Fumesucker]

32. That depends on the transmission..

With a Continuously Variable Transmission (CVT) engine speed does indeed stay the same while vehicle speed changes, at least some of the time.

[hokies4ever]

20. Also, does drag vary linearly with speed?

{hint: the answer might be no} :rofl:

[hokies4ever]

18. Also, theoretically the best gas mileage should be around

the speed where the car is in its highest gear, the car is in overdrive (if the car has the feature), and the torque converter is locked (assuming it's an automatic).

[Fumesucker]

22. It depends on how good your theory is..

Some theories fit the observed facts better than others.

[hokies4ever]

24. How does drag vary with speed

Is it linear? (hint: the answer might be no)

Drag is not linear with speed, plain and simple. Surely you can find an equation for the drag in your physics book, right? Does it vary linearly with speed? Nope. And if you don't like that theory, then do wind tunnel tests for cars show that drag varies linearly with speed?

You do understand why increasing speed when you're in the highest gear, taking into account the fact that drag does not increase linearly with speed, means that you'll get a lower gas mileage, right?

[Aviation Pro]

30. Can't talk automotively but I sure as hell can talk aerodynamically...

...drag increases as aircraft move faster through the atmosphere (this is skin friction drag); drag also increases as the aircraft slows behind the power curve (this is induced drag). Either way, you need more gas to maintain the equivalent level of lift for straight and level flight.

[Fumesucker]

31. Drag is not the only variable involved in efficiency..

Do you even know what BSFC is?

[hokies4ever]

37. summa cum laude engineering undergrad

currently a doctoral student at MIT, engineering also. I guess I'm not as dumb as you thought I was. :rofl:

Oh, and physics was always one of my best subjects, hehe.

My simple explanation as to why I disagree with you is that the drag force on a car does not vary linearly with speed.

I know your bigger point is that SUVs suck at gas mileage. Although true, the people have already bought them. It's not like they can just go in today and trade in their SUV without any economic penalties. Hopefully they learn their lesson and choose a different vehicle next time. :patriot:

[Aviation Pro]

41. Cool beans...

...so how come the engineers have not designed vehicles with ligher, stronger material to bring weight down? Oh, I know, because the effing stupid morons in markets have told the engineers that Americans want big, heavy, gas sucking V-8s.

No we don't.

[hokies4ever]

45. Hate to break it to you, but it's all about economics.

Engineers aren't in the business of making things better, but making money for companies. One of the biggest pieces of advice given to engineers before job interviews is when asked why you want the job, say to make money for the company, not to discover science or anything along those lines. Same with most industries as well. You think pharmaceutical companies create drugs because they care about the health of people? They do it for the dough. Capitalist society at its best. :rofl:

[Fumesucker]

43. On the internet nobody knows you are a dog..

Actually my bigger point is that not all automobiles invariably get better mileage the slower you go..

And I can explain why.

[hokies4ever]

46. Surely you're not going to argue

that SUV drivers should drive faster to save gas money, are you? That's an awfully lonely argument. :rofl:

[Fumesucker]

50. Why do you put words in my mouth?

It seems to me that intellectual honesty should be a trademark of someone as intellectually gifted as yourself.

[hokies4ever]

51. You're intellectually stubborn

Hillary would apologize or admit a mistake before you would. :rofl:

You started a vent thread based on a fallacious argument. In my line of work, you call out somebody for stuff like this.

Please don't continue this argument until you look up how drag force varies with velocity. I know I've mentioned this many times already, yet you refuse to read this.

[Fumesucker]

53. What "fallacious argument"?

I'm well aware that aerodynamic drag varies with the square of the velocity and, since you are still a student, I have known this since well before you were born.

Tell me *exactly* what it is you think I'm wrong about, then we can argue.

[hokies4ever]

55. Here's what YOU said

"I noticed that nearly all the SUCKVs were driving about 10 miles slower than the posted speed limit. Now I hate to burst their stupid gas hog bubble but they should have studied harder in high school then they would have known that f=ma and would have figured out that they still have to move all that mass."

It's intellectually dishonest. These driver aren't stupid as you insinuated ("should have studied harder in high school"). F=ma is a faulty force balance. The net force on the SUV will be 0 anyway, because it will be driving at a constant speed and not accelerating, whether it be 55, 65, or 75 miles per hour. If you're going to mention forces, you should be aware that the drag force varies with the square of velocity, not linearly with velocity. They ARE saving gas by driving slower. Intellectual vent threads should be thought out before they are made.

Congrats on being older than me. Choc chip or oatmeal? What kind of cookie do you want? Perhaps a gold star too? I'm not getting paid to educate you, so feel free to use 'The Google' if you have anymore questions. :rofl:

[Fumesucker]

56. Go back and look,.. It wasn't me that wrote that passage. n/t

[hokies4ever]

57. I stand corrected

:patriot:

But you still defended this intellectually horrible position. :rofl:

[Fumesucker]

58. I did not "defend that intellectually horrible position"..

What I said, and I stand by it, is that not all vehicles will always get better mileage by slowing down.

[hokies4ever]

59. The vehicles in question were named though

as SUVs. If any vehicle should slow down, it should be these. They clearly have large wind profiles.

[Fumesucker]

60. You are making blanket statments

I'm trying to be "nuanced"..

I guess you think nuance is bad?

Oh and I mentioned a specific SUV that gets worse gas mileage at 35 mph than at 65 mph.

[hokies4ever]

62. Were they driving at 35mph instead of 65 mph on the freeway?

Are you even thinking before you're writing now? :rofl:

[TrogL]

38. Best gas mileage

Is the bottom revs of the highest gear your vehicle has.

That's the problem with city driving. You never get into 4th gear on an automatic.

[hokies4ever]

40. Agreed

Although I would point out that one of the major reasons that highway mileage is much better than city mileage is because of the stop-and-go driving instead of just straight non-stop driving. Accelerating and braking use up a lot of fuel too.

[Fumesucker]

52. Not necessarily and not always...

Smaller, lighter and less powerful cars tend to get better efficiency the slower you go..

Larger, heavier and more powerful cars do not always act in the same manner.

There are a large number of variables in automotive fuel efficiency and everyone here seems to wish to concentrate on only one or two of the variables.

A 2008 Z06 Corvette with a 7.0 505 hp engine will get 30 mpg or better on the highway at 70 mph..

[Ganja Ninja]

54. I wish they would ban all driving for 1 day a week except for ...

Hybrids, Electric Cars, Motorcycles and Scooters and of course anyone that needs to go to work such as police, fire department, EMS and hospital workers.

They could start out doing it one day a month then increase to 2 days a month and so on.

[fascisthunter]

61. Too Bad Even the Small Vehicles are Gas Guzzlers

I'm for driving small, I have a small car, but these companies manufacturing them, manufacture them to be inneficient.While I agree it helps to buy smaller, lighter more compact, we need to get big oil away from the automotive industry because they are both colluding with each other. Even small vehicles are gas guzzlers... we have the technology to drive more efficiently, but the makers of these cars aren't willing to create them to be that fuel efficient.

There is a lot of investing in both industries.

[hokies4ever]

64. As Chris Rock will say

We can send a man to the moon but can't make an El Dorado where the bumper doesn't fall off. :rofl:

[fascisthunter]

65. genius

what's even funnier, is our reality writes the guy's material, all he has to do, is give the expression.

[hokies4ever]

66. I loved his line about the superdelegates:

Whoever heard of superdelegates before a black man ran for President? :rofl:

[fascisthunter]

67. lol....

now see that's funny but so damn true it hurts.

[gatorboy]

63. They were probably on their cell phones. n/t