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

[DawnCt1]

Back in the 70's, speed limits were lowered to 55 mph to conserve fuel. I have tried driving at 55 mph, increased my speed to 62 mph and have seen no difference in the rpms, hovering between 1800 and 2100. Past 65 mph, there is a slight difference up to 70 mph.
With DH's car, his is a manual. I can easily keep the rpms at around 1500 to 1800 rpms by shifting into higher gears, all the way up to 70 mph. So with the new engineering, transmissions, etc. Is the call for 55 mph just "feel good stuff"?

 

[dejr_8]

I've been wondering when the call for 55 will return. "They" will still argue that if you are getting X mpg @70 mph you will get X+Y mpg @ 55 mph so for the good of the country we need to decrease the speed limit.

 

[DawnCt1]

I've been wondering when the call for 55 will return. "They" will still argue that if you are getting X mpg @70 mph you will get X+Y mpg @ 55 mph so for the good of the country we need to decrease the speed limit.

That will be the argument but with the advancements in motor/transmission technology, is it factual?

 

[dejr_8]

That will be the argument but with the advancements in motor/transmission technology, is it factual?

Yes - it is fact.

 

[lovin diz]

my car has a digital "ave mpg" computer screen on it, (2009 Toyota corolla) and believe it or not if i go 55mph on the interstate, i average about .3 mpg less than i do when i go 65mph. Go Figure

 

[dejr_8]

my car has a digital "ave mpg" computer screen on it, (2009 Toyota corolla) and believe it or not if i go 55mph on the interstate, i average about .3 mpg less than i do when i go 65mph. Go Figure

Each car will exhibit a different relationship between MPG and MPH. For your car, engine and transmission gearing 65 MPH could be the optimum. For a full size P/u, it is probably less.

But on average across all vehicles, going 55 will give better mileage than 65.

 

[DawnCt1]

my car has a digital "ave mpg" computer screen on it, (2009 Toyota corolla) and believe it or not if i go 55mph on the interstate, i average about .3 mpg less than i do when i go 65mph. Go Figure

I use the same feature on the CTS and 62 mph gives me the best overall economy. When I drive DH's car, I watch the rpms and keep them below 1800.

 

[BunsenH]

The aeroedynamics of car designs deteriorate quickly at speed above 55 mph. The increase in wind resistance forces the car to use more power to maintain the higher speeds. Physics don't lie or give any breaks.

Drivin' 55 (sorry Sammy Hagar) vs. 70 will save 10-15% in mpg.

 

[GeorgeG]

I think driving style probably has as much to do with gas consumption as does speed. An aggressive driver is likely to use more gas.

The best thing we can do to save gas is to curb our use of the car. Again, that will vary according to each person's needs, but the best studies show that cars tend to use a lot less gas while in the garage or driveway.

Seriously, though, we all can probably limit our driving at least a little.

 

[cteddiesgirl]

I think driving style probably has as much to do with gas consumption as does speed. An aggressive driver is likely to use more gas.

The best thing we can do to save gas is to curb our use of the car. Again, that will vary according to each person's needs, but the best studies show that cars tend to use a lot less gas while in the garage or driveway.

Seriously, though, we all can probably limit our driving at least a little.

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.

 

[Mr Man]

In my truck, I can get nearly 20mpg on the highway if I drive no faster than 65mph. I Can't Drive 55 (thanx Sammy Hagar).

In the city, I get no better than 15mpg no matter what I do.

The only thing I see happening if we go back to 55mph limit is a dramatic increase in revenue to local Polic Depts due to tickets.

 

[ICF]

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?

 

[CapeCodTenor]

Being from New Mexico, I hope they don't return the speed limit back to 55 mph. Try driving through New Mexico, Texas, Arizona or any other large western state at 55 mph, it'll drive you insane.

 

[legalsea]

Back in the 1970s we had a gasoline shortage. Hence, the lower speeds were mandated.

We do not have a gasoline shortage today. You may buy all the gasoline you wish. So there is no reason to lower the speed limit.

 

[CPT Tripss]

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?

Time has nothing to do with miles per gallon . . . driver 1 gets 25 mpg, uses 20 gallons driver 2 gets 20 mpg uses 25 gallons.

That said, I didn't like 55 back in the dark ages and I don't like it now. My last long trip (1000 plus miles) I averaged a little under 75 mph, excluding stops. I got a little over 37 mpg . . . fuel efficient vehicle, tuned, good tire pressure and windows up . . . a/c for about 1/2 the time.

 

[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?

Do you mean same driver, same car taking 2 different trips? What mpg does the car get at those speeds?

Need that info to calculate gallons per hour and answer your question.

 

[squirrlygirl]

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?

Yes, because gas consumption is measured in miles per gallon, not miles per hour. So it will take longer, but you used less gas each mile despite it taking longer to cover it. Kind of like me and my grandpa. I can run to the mailbox while he shuffles. I'll use more energy running than he'll use walking, even though it'll take him 3x as long.

As for driving slower, DH slowed down from an avg. of 76 down to 67 on his (freeway) commutes, and his mpg went from 32 mpg up to 36 mpg (he has a Chevy Cobalt coupe) IIRC, each car has an optimal speed for best mileage, which varies between 55 and 65 somewhere. My minivan has a real-time mileage guage, and it appears I do best around 62.

But as I dropped out of physics halfway through the year to meet a government requirement, I may be completely mistaken.

 

[tlens]

My brain hurts.

Let's confuse you even more and convert to kilometers.

 

[Rigatoni]

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?

But here is a more important question:

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

 

[tlens]

But here is a more important question:

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

They weigh the same. A pound is a pound.

But I'll take the gold.