55 mph vs. 65 mph, Is it Relevant Today?

[Golf4food]

With modern engines the biggest help would come from people not gunning it after a red light to race away as fast as possible. Rapid accelleration burns far more gas than driving at high highway speeds ever will. Then do the @#$% speed limit and stop driving like maniacs.

 

[BunsenH]

Here is an example, which one one uses less fuel?? -- Any thoughts?

Driver 1 -- Drives 500 miles @ an average speed of 55mph. His journey takes 9.1 hours.

Driver 2 -- Drives 500 miles @ an average speed of 70mph. His journey takes 7.1 hours.

So....while driver #1 likely got a better mpg due to driving 55, did he really save gas if he was driving 2 hours more then driver #2?

To achieve closure (this retired engineer needs brain exercise):

Let's assume that the car gets 30 mpg at 55 mph, and 25.5 mpg (-15%) at 70 mph.

Trip 1 - 16.7 gallons of gas (1.83 gal/hour)

Trip 2 - 19.6 gallons of gas (2.76 gal/hour)

(If there is only a 10% penalty at 70 mph, gas consumed is 18.5 gallons [2.26 gal/hour].)

So....Trip 2 saves gas (3 gal = $12)....but takes an additional 2 hours. The driver needs to decide if two hours of their time is worth the extra money

 

[Mr Man]

But here is a more important question:

What weighs more, a pound of gold or a pound of feathers?

A Duck!

A Witch!! Burn!! Burrrrrn!

 

[worm761]

Problem is most Americans won't give up their car for anything. I know a lot of people who have to drive when they're only going 2 or 3 blocks.

I can't tell you how many nasty looks, nasty comments and how many times I see the finger when I'm walking home from the bus stop at night. Last night alone I had one nasty drive by comment and another guy actually barked at me. Just because I'm walking instead of sitting on my lazy butt and not spending $80 a week on gas.

I take offense to this. I use my car to go everywhere I have to. It has NOTHING to do with being lazy and everything to do with the safety of me and my son! Just because you walk and other people drive doesn't make them lazy. Nor does it make you better than them. You are making a choice. So are they. Don't judge. I will not walk where I do not have a sidewalk to walk on. It is not safe to walk on the side of the road. You endanger yourself and those around you.

 

[Golf4food]

A Duck!

A Witch!! Burn!! Burrrrrn!

I was milliseconds away from doing almost the exact same post but chickened out, lol.

 

[cteddiesgirl]

I take offense to this. I use my car to go everywhere I have to. It has NOTHING to do with being lazy and everything to do with the safety of me and my son! Just because you walk and other people drive doesn't make them lazy. Nor does it make you better than them. You are making a choice. So are they. Don't judge. I will not walk where I do not have a sidewalk to walk on. It is not safe to walk on the side of the road. You endanger yourself and those around you.

Where did I say everyone? Did I not state those that drive when they're only going 2-3 blocks?

And actually, it's really not much of a choice for me since I can't even afford a vehicle. But I still would walk instead of drive if I'm only going 2-3 blocks. It's good excercise and I wouldn't be wasting gas and money.

Oh. I also have no sidewalks at all where I walk. I don't see where I put anyone in danger but myself. And I do keep my eyes towards on coming traffic and keep my ears on any traffic on the opposite side coming behind me. I trust no one behind the wheel with my life. If need be, I can jump out of the way immediately. I've done this for at least 12 years. I have never been hit yet.

If people look where they're going and pay attention to the roads and what others are doing around them instead of paying attention to their phones, radios, other people in the vehicle, etc., there would be a lot less accidents.

I take offense towards those drivers that give me the finger, give me nasty looks or give me nasty comments just because I'm walking instead of driving.

Taking public transportation and/or walking actually has a social stigma attached to it. So, most people will not give up their cars for any reason.

Anyway, back to the real topic.

 

[DawnCt1]

Today's experiment. Usually when I go on a long trip, Mass Pike most recently, I set the speed control at 67 and leave it there. This keeps the RPMs about 2200-2300. I average 25 mpgs with my 6 cylinder CTS. Today I went grocery shopping, got on the highway and drove 10 miles. I set the speed control at 58. The RPMs hovered at just under 2000. Average 32. Of course, as soon as I got off of the highway, stopped at three stop signs and two traffic lights with an average speed at that time of 40 mph for five miles, it lowered my mpgs to 29. Still, not too bad. That is also with AC going.

 

[Barbossa]

I'm all for going back to a 55 mph speed limit...so I can drive at that speed without causing traffic jams. I'm doing the hypermiling thing, the slower the better (I hear 40 mph is the speed where most cars get their best gas mileage, not that I want to go that slow). As far as commute time, it makes little difference for me.

 

[Barbossa]

Here is an example, which one one uses less fuel?? -- Any thoughts?

Driver 1 -- Drives 500 miles @ an average speed of 55mph. His journey takes 9.1 hours.

Driver 2 -- Drives 500 miles @ an average speed of 70mph. His journey takes 7.1 hours.

So....while driver #1 likely got a better mpg due to driving 55, did he really save gas if he was driving 2 hours more then driver #2?

As a previous poster described, it's primarily about aerodynamics/wind resistance. Physics 101 says that Energy = Force x Distance. The faster you drive, the greater the force due to wind resistance. Thus, for a given distance, your car expends less energy if it goes slower. Of course there are other factors involved i.e. friction, engine efficiency. But aerodynamics is the dominant factor.

 

[DawnCt1]

Problem is most Americans won't give up their car for anything. I know a lot of people who have to drive when they're only going 2 or 3 blocks.

I can't tell you how many nasty looks, nasty comments and how many times I see the finger when I'm walking home from the bus stop at night. Last night alone I had one nasty drive by comment and another guy actually barked at me. Just because I'm walking instead of sitting on my lazy butt and not spending $80 a week on gas.

Unless you are walking in the middle of the road, I can't imagine anyone would care. I have never seen anyone give a pedestrian a nasty look unless they were obstructing traffic. Not everyone can "walk". If one works odd hours, has mandatory overtime, doesn't live on a bus route, lives in the suburbs or a rural area, mass transit isn't an option. It isn't an option for parents with children with after school activities, those who must transport elderly parents, those who must grocery shop for a large family, etc.

 

[CPT Tripss]

Today's experiment. Usually when I go on a long trip, Mass Pike most recently, I set the speed control at 67 and leave it there. This keeps the RPMs about 2200-2300. I average 25 mpgs with my 6 cylinder CTS. Today I went grocery shopping, got on the highway and drove 10 miles. I set the speed control at 58. The RPMs hovered at just under 2000. Average 32. Of course, as soon as I got off of the highway, stopped at three stop signs and two traffic lights with an average speed at that time of 40 mph for five miles, it lowered my mpgs to 29. Still, not too bad. That is also with AC going.

Those mpg guages are not necessarily accurate, but they do give a good indication of relative fuel efficiency.

Do you double check by calculating mpg each time you fill the tank?

 

[HOGFAN]

all I know is that lately I've had LOTS more company in the slow lane.

 

[BunsenH]

Those mpg guages are not necessarily accurate, but they do give a good indication of relative fuel efficiency.

Do you double check by calculating mpg each time you fill the tank?

I've checked mine a few times and was pleasantly surprised to see that it was within 2% of the calculated value.

 

[Charade]

But here is a more important question:

What weighs more, a pound of gold or a pound of feathers?

What is the airspeed of a swallow?