I'm having trouble convincing my dad + sister that..

[imported_goku]

I've heard over and over that you're not suppose to go over 65mph and 55 is the best to get good fuel economy from 'articles' and the such yet I've heard of people who say they get better mileage at 90mph for their car. My stance on the subject is that for trucks, over 55 will definately kill mileage unless really aerodynamic and for cars, it really just depends. So what is it ATOT? How can I convince them of otherwise.

It's funny really, I told my dad, if you don't believe me, why don't you just try it out, and over and over they kept reciting how 'scientific proof and studies yada yada yada' can't be wrong, and so on. Funny that my dad told me this, statistics are an amazing thing, you can make them say what ever you want if you get the right data.

I just don't see how driving a car two different speeds to LA from SF wouldn't be able to prove with out a doubt whether or not it's true.

 

[BigJ]

Gear Ratio.

 

[sixone]

Are you sure they CAN be convinced? Is this argument worth having?

 

[BoomerD]

Maybe because, with only a few exceptions, they are right. Higher speeds use more fuel.
http://www.fueleconomy.gov/feg/driveHabits.shtml
"While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

As a rule of thumb, you can assume that each 5 mph you drive over 60 mph is like paying an additional $0.20 per gallon for gas.


Fuel Economy Benefit: 7-23%
Equivalent Gasoline Savings: $0.20-$0.67/gallon "

 

[jagec]

It totally depends on the engine, the gearing, and the aerodynamics of the car. All cars have their own most efficient speeds, but they tend to be designed around ~60MPH, I'd say.

 

[potato28]

Is it worth arguing about? If they have a different vehicle that you do then its a lost cause...

 

[imported_goku]

I agree with all the posts made in this thread thus far. Car that comes to mind at the moment is the ford taurus.

 

[jagec]

Originally posted by: BoomerD
Maybe because, with only a few exceptions, they are right. Higher speeds use more fuel.
http://www.fueleconomy.gov/feg/driveHabits.shtml
"While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.

The question is, do you trust the government when it comes to the facts?

Also, driving the limit is NOT safer, going ~4-8 over is the safest, assuming good roads and weather.

Here's evidence, if you can wade through it...you want to stay within the 85th percentile for greatest safety.

 

[HamburgerBoy]

Originally posted by: sixone
Is this argument worth having?

Originally posted by: potato28
Is it worth arguing about?

Isn't this the person who argues with his mom over iPod software being installed on her hard drive? Nothing is too trivial to argue about in goku's mind.

 

[WiseOldDude]

The reason you are having trouble convincing them is because you are WRONG!

 

[sixone]

Originally posted by: HamburgerBoy

Originally posted by: sixone
Is this argument worth having?

Originally posted by: potato28
Is it worth arguing about?

Isn't this the person who argues with his mom over iPod software being installed on her hard drive? Nothing is too trivial to argue about in goku's mind.

I have no fracking idea. I'm only here 'cause TFNN is down.

Hi, llama!!!

 

[Fritzo]

If your car is geared for it, it can happen. Most cars get their best milage between 45 and 65 though.

I think high performance cars would only be geared that high (maybe a 6 speed or something). You're trying to argue that an obscure case applies to everyone.

 

[sniperruff]

Originally posted by: goku

I just don't see how driving a car two different speeds to LA from SF wouldn't be able to prove with out a doubt whether or not it's true.

as soon as one of the many variables such as weather, temperature, wind direction/speed, traffic, mass of occupant(s), quality of gas, time of the are not exactly identical, you wouldn't be able to prove anything just like you can't prove how apple is evil.

 

[BobDaMenkey]

The optimal speed of all cars will be different. However to side with your folks, during a trip to LA over the I-10 I averaged 24mpg, after the A/C broke while doing 75ish mph. After a weeks worth of driving to and from ASU (22ish miles of highways, 5 of actual streets) doing no more than 65mph, I averaged 27-28mpg without the A/C on.

 

[pcnerd37]

I did the math on this a couple years ago and found that my best was around 40mph.

 

[Cattlegod]

techically wouldn't the most efficient speed be as follows:

highest gear
lowest hp rpm on the car (probably just above idle)

most cars that ends up being around 40 mph in a 5 speed or so.

 

[imported_goku]

Originally posted by: sixone

Originally posted by: HamburgerBoy

Originally posted by: sixone
Is this argument worth having?

Originally posted by: potato28
Is it worth arguing about?

Isn't this the person who argues with his mom over iPod software being installed on her hard drive? Nothing is too trivial to argue about in goku's mind.

I have no fracking idea. I'm only here 'cause TFNN is down.

Hi, llama!!!

While that is true, having iTunes installed on a machine and then shortly after getting complaints from her that it's unreliable only infuriates me due to my blind hatred towards apple. Apple is facist and I hope the company is razed to the ground.

 

[imported_goku]

Originally posted by: Cattlegod
techically wouldn't the most efficient speed be as follows:

highest gear
lowest hp rpm on the car (probably just above idle)

most cars that ends up being around 40 mph in a 5 speed or so.

But... the car is the least efficient at that RPM, that would be more true in a diesel than a gasoline engine. You'd need to be at peak torque which is significantly higher in a gasoline engine, 4400RPM in my car.

 

[Eeezee]

Originally posted by: goku
I've heard over and over that you're not suppose to go over 65mph and 55 is the best to get good fuel economy from 'articles' and the such yet I've heard of people who say they get better mileage at 90mph for their car. My stance on the subject is that for trucks, over 55 will definately kill mileage unless really aerodynamic and for cars, it really just depends. So what is it ATOT? How can I convince them of otherwise.

It's funny really, I told my dad, if you don't believe me, why don't you just try it out, and over and over they kept reciting how 'scientific proof and studies yada yada yada' can't be wrong, and so on. Funny that my dad told me this, statistics are an amazing thing, you can make them say what ever you want if you get the right data.

I just don't see how driving a car two different speeds to LA from SF wouldn't be able to prove with out a doubt whether or not it's true.

That would be a scientific test that would prove whether or not 55 is better than 75 (or 90 or whatever). It's also a scientific test that has never been done to my knowledge

 

[tbike06]

Originally posted by: goku

Originally posted by: Cattlegod
techically wouldn't the most efficient speed be as follows:

highest gear
lowest hp rpm on the car (probably just above idle)

most cars that ends up being around 40 mph in a 5 speed or so.

But... the car is the least efficient at that RPM, that would be more true in a diesel than a gasoline engine. You'd need to be at peak torque which is significantly higher in a gasoline engine, 4400RPM in my car.

dont necessarily need peak torque, just enought so that the engine doesnt bog or slow down, maybe in the middle of the curve.

 

[MX2]

Arent you like 13?

 

[Eeezee]

Also, it really depends on the car. Let's say you have two of the exact same model of car in the exact same gear. One car is going 45 mph and the other is going 60. If you neglect gas use for starting the engine and keeping it running, the car going 45 mph will have a better fuel economy than the car going 60. I don't know enough about engines to tell you for sure, I'm just going off of a very basic drag principle. The faster your car goes, the harder drag will push against you. It's the principle that governs terminal velocity in freefall. You can't go faster than a certain speed in freefall because air friction pushes you up with the same force as gravity pushes you down once you reach a certain speed.

Car fuel economies are much more complicated than that. You can't simply say "faster car make more drag, der."

So how about you conduct that test that you mentioned? It'd probably take $200 to do enough trial runs. Do it 3-5 times per speed you want to test for mileage, that should give you a decent sample set. Try 55, 70, and 85 to see which gives you the best fuel economy. I am certain you will not have the best mileage at 85, that much is clear because at those high speeds you're no longer fighting against a force proportional to velocity, you're fighting against a force proportional to velocity squared!

 

[Nebor]

Really depends on the gearing of the car. My Volvo is a much, much faster car than my Acura, but it will get 25mpg at 60mph and only 16mpg at 100mph. While the Acura gets 32mpg at 60mph and 26mpg at 100mph.

I know this because I drive fast a lot.

 

[RelaxTheMind]

If you take a look at a more simpler aspect... The amount of gas getting dumped into the engine is also highly dependant on how much gas you use/waste. Try driving around like a grandma and you would be suprised how much gas you will save.

So technically all the factors in driving fast (drag, gas pedal, slowing down and speeding up behind slow people, etc) point to faster=less mpg. put it this way... go in a pool and slowly push your hand forward on top of the water... then push it faster and see how much harder it is to do requiring much more force and energy. Same rule applies to cars with the force of air and gravity.

The arguments i see coming from the OPs end is similar to how a tractor trailor would be. It uses a lot more gas in its first 5 gears to build up its momentum but after it breaks that coefficient of friction its randy dandy.

 

[SilthDraeth]

Find that point where your car starts to shake real bad, and push it just past that point, where the ride is perfectly smooth then. That is your optimum speed to obtain the best MPG, above or below that "shaking point". The shaking point is about the worst MPG you could get.

Thats my opinion, though it isn't tested.