We don't need hybrids,.. we need 55MPH! - a long winded ramble.

[JoLLyRoGer]

Remember the old national maximum speed law of the 70's and 80's when 55MPH was the posted speed limit on all major highways and Interstates brought about by the gas crisis of the 70's?

Nixon believed a car's peak efficiency was realized between 40 and 50 MPH. This week I've been putting it to the test.

Typically I drive a older Honda accord for my commuter car that gets 30+ MPGs so I don't think much about fuel economy. It's decent enough and I just drive.

Well, the Honda has broken down for about three weeks now forcing me to drag out my weekend toy and put it on commuter duty until I can get around to repairing the other car.

The weekend warrior happens to be a 2008 Mustang I've modified with a supercharger, larger injectors, oversize tires, duel fuel pumps, a high flow exhaust system, and 4.10 rear axle gears. It dyno's 460ish RWHP and using a standard 15% drive line loss estimate puts it around 530HP at the flywheel.. Well into GT500 territory. The result is a holy terror that gives not a f**k about fuel economy (indeed that's what my Honda is for).

Now, all things considered the car still averages between 18-19MPG HIGHWAY driving 'normal'.. not hot rodding it, but normal habits and normal highway speeds. Using cruise, etc... Well at $3.80/gallon for premium and a 35 mile one way commute that gets expensive. Not such a concern when tearing it up a couple times a month at a weekend Autocross event, but for daily driving it puts a hit in the wallet. So I decided to self impose a 55MPH speed limit for myself over the past few days.

The result? I'm currently averaging 23-24mpgs.. That's an approximate 27% increase in mileage from just easing off the throttle.. Not bad for a 500HP fire breathing devil-car.. Think if what returns you could see in something fuel efficient to start with, and it maybe adds 5 min onto my total commute time? Sure it may piss off other motorists who get stuck behind me, but they're not pouring $$$ into my gas tank, and that's what the left lane and passing zones are for so F- em.

I hate to say it, especially cause I have the go-fast bug in my blood, but 55MPH might not have been such a bad idea back in the day - and definitely not today either. If we all used a 1/4 - 1/3 less gas in our vehicles the laws of supply and demand take over, prices at the pumps drop, shipping and manufacturing on every-last-thing drops. Cost of living drops, people start spending more, traveling more, the economy gets a boost (I think you know where I'm going with this..) Of course it's all just an altruistic pipe dream.

Here in the real world people would never go along with it (just like they didn't back then) or even if they did the oil futures investors on Wall Street would just artificially inflate oil prices to pad their profit margins thus offsetting any drop in demand so the whole point becomes moot.

But.. in theory it could work and go a long way toward reducing our foreign oil dependency and cutting shipping and manufacturing costs of a lot of goods that require a gallon of gas to be manufactured, farmed, transported, etc.. which pretty much encompasses everything and anything.

OK, I'm done with it... Let the nay-sayers take over and chime in how it's dumb, and won't work, and the politicians will corrupt it, it was tried before and it failed then, blah blah blah..... Like I said I'm speaking theoretically/hypothetically. In the real world people are selfish ass-clowns by and large and could give two shits less.. I get it.

Discuss.
-JR

 

[bucwylde23]

55 MPH is fine on roads with a 55 MPG speed limit. Stay out of the left lane on the interstate.

 

[AyashiKaibutsu]

So from your one test with a car far outside the average and you think national policy should be based on it?

 

[CLite]

I hate to say it, especially cause I have the go-fast bug in my blood, but 55MPH might not have been such a bad idea back in the day - and definitely not today either. If we all used a 1/4 - 1/3 less gas in our vehicles the laws of supply and demand take over, prices at the pump drops, shipping and manufacturing on every-last-thing drops. Cost of living drops, people start spending more (I think you know where I'm going with this..) Of course that's all just an altruistic pipe dream.

1/3 less gas while cruising on highway for a random car. Let's say about 1/50th of the total gasoline used in the USA is spent on interstate cruising.

You have saved 1/150th of the gasoline consumption, which may make a slight impact at the cost of pissing off all the daily commuters (try driving 55 on NJ highways and you will get rear-ended in the morning/evening commutes).

Also I drive a honda civic and over the course of commuting 60 miles/day for years I have tried many different techniques (more out of curiosity than cost savings), and I pretty much have never been able to tell any difference. Your example is a bit extreme with such a high horsepower car.

 

[Fausto]

55mph is entirely too slow when making a long drive. If you want to save gas, go right ahead and drive 55, but making it law (again) is just stupid.

 

[overst33r]

So from your one test with a car far outside the average and you think national policy should be based on it?

He is simply validating what we already know. Physics.

Everything else equal, one WILL use less gas if going 55mph instead of 70mph. Doesn't matter if its a 800hp monster or a 100hp civic.

 

[HAL9000]

55MPH is slow, the national speed limit over here is 70MPH and that makes sense.

 

[JoLLyRoGer]

So from your one test with a car far outside the average and you think national policy should be based on it?

I'm just spitballing ideas.. All I'm really saying is I backed it down and got a nice bump in fuel mileage.

 

[FoBoT]

ok, Jimmy Carter, i'll take that under advisement

 

[AyashiKaibutsu]

He is simply validating what we already know. Physics.

Everything else equal, one WILL use less gas if going 55mph instead of 70mph. Doesn't matter if its a 800hp monster or a 100hp civic.

That assumes time spent traveling is equal (hint: faster cars spend less time traveling). Cars of the past might have been at their peak gallons per mile at 55, but without looking at how the average car actually performs now you have no way of knowing what the ideal is. I'm not saying he's wrong; I'm saying his methods for determining how things should be is stupid.

 

[NikolaeVarius]

Well its more or less scientific fact that most cars are most efficient at around 45-55 mph, after that gas efficiency drops extremely, extremely quickly.

It's the matter of getting people to drive at that speed that is the issue

 

[busydude]

I'm just spitballing ideas.. All I'm really saying is I backed it down and got a nice bump in fuel mileage.

We have these 1000cc cars in India which can do 50 MPH(Can take ages to get there though) and are rated to give about 20KMPL or 75MPG.

There is also this car known as Chevrolet Beat.. the diesel variant of this car is rated for 87MPG. On top of that it costs about $8k. Needless to say, almost all of the cars will fail crash tests here in the US.

 

[scannall]

It's a bad idea. The interstate system was built for 85 Mph as part of the design spec. Speed limits in most states are set by averaging the speed that people drive, up to the state maximum. (Curse you Oregon, 65 really does suck out in the middle of nowhere).

By forcing a low number you are making the road less safe. Freeway accidents are caused more often by speed differential, than the actual speed that people are driving. If everyone is going 80, then there is no speed differential. If the speed limit is 55 you are going to have some following it. Some just pushing by 5-10 over and others driving at what would normally be a safe speed for that section of freeway of say 80. Lots of opportunities for crashes.

As a 1 car anecdote of my own. Driving from Colorado to Oregon in my older Volvo 740 I got 27 Mpg. And that's doing 80-85 on the freeway, 5 over the speed limit. The speed limit in Oregon is 65, and that is what I drive at here. I average 29. Not a very significant savings.

 

[Beev]

How about if shitty greedy car companies put more effort into overall efficiency so we could go 75 and get the same results you see by going 55? Is that too much trouble?

Fuck yes it is. There's no money in efficiency.

 

[IronWing]

I agree with everything you've written concerning mileage. 55 would save tons of fuel, tons of money, and tons of lives. However, I still like 75. 75 means most folks are doing 75-80. I noticed that in west Texas where the limit is 80 that most folks still did 75-80. The vast majority of vehicles on the road just can't maintain higher speeds in the long haul or the drivers find the handling too squirrelly at higher speeds. I grew up with 55 so didn't understand the burning, passionate hatred for the 55 limit expressed by my elders. Now I would have that same resentment with a return to 55. Once you've gotten used to higher speeds, going back seems like a complete waste of time. Also, oil is finite. Any that we don't waste will just get wasted by the Chinese. Might as well be me at the wheel.

 

[Red Storm]

Well its more or less scientific fact that most cars are most efficient at around 45-55 mph, after that gas efficiency drops extremely, extremely quickly.

Really? Once a week I have to drive from DC to Annapolis and I average 70-80 MPH the whole way there and my MPG is at it's absolute best on these trips.

 

[Squisher]

I hope you realize that the number one influence on the prime range for fuel efficiency for a vehicle is the differential ratio. If you were to restore your differential to stock (3.73?) you would probably see the speed at which you drive for best fuel efficiency rise to 65 mph.

 

[96Firebird]

I hope you realize that the number one influence on the prime range for fuel efficiency for a vehicle is the differential ratio. If you were to restore your differential to stock (3.73?) you would probably see the speed at which you drive for best fuel efficiency rise to 65 mph.

This is what I was going to post... Your 4.10s are killing your mileage over 55. Most cars have a lower ratio, and get the best fuel economy at higher speeds (to a certain point).

 

[HumblePie]

He is simply validating what we already know. Physics.

Everything else equal, one WILL use less gas if going 55mph instead of 70mph. Doesn't matter if its a 800hp monster or a 100hp civic.

Nope. I use less gas going 70 instead of 55. Proven this every time. I get 18 MPG if most of my driving is 55 and I get 22 if most of my driving is 70-75.

So I invalidate yours and the OPs claim. Anecdotal evidence should not make a national policy. If you feel like driving 55 on a 70 highway, then feel free. Just stay out of the left hand lane because that's where I'll be.

 

[manimal]

I just called Sammy Hagar and he disproves of this message.

 

[the DRIZZLE]

I agree with everything you've written concerning mileage. 55 would save tons of fuel, tons of money, and tons of lives. However, I still like 75. 75 means most folks are doing 75-80. I noticed that in west Texas where the limit is 80 that most folks still did 75-80. The vast majority of vehicles on the road just can't maintain higher speeds in the long haul or the drivers find the handling too squirrelly at higher speeds. I grew up with 55 so didn't understand the burning, passionate hatred for the 55 limit expressed by my elders. Now I would have that same resentment with a return to 55. Once you've gotten used to higher speeds, going back seems like a complete waste of time. Also, oil is finite. Any that we don't waste will just get wasted by the Chinese. Might as well be me at the wheel.

This. We could also all turn the heat down or AC down in our houses but we don't do that either. Personally my time is more valuable than the fuel savings.

 

[AstroManLuca]

How about if shitty greedy car companies put more effort into overall efficiency so we could go 75 and get the same results you see by going 55? Is that too much trouble?

Fuck yes it is. There's no money in efficiency.

You can't change the laws of physics. Gas mileage drops off above 55 because of air resistance. Cars are always becoming more aerodynamic but there's only so much you can do. Reducing weight could also improve fuel economy, but gas mileage will always be better at 55 than it is at 75. The best they can do is try to minimize the amount of fuel economy drop-off above 55.

If you think about it, it's amazing cars these days get as good mileage as they do given they generally weigh a lot more than cars of decades past. The more streamlined shapes and more efficient engines have been good enough to offset the weight gain, but I do agree that I'd like to see mileage start to go up instead of staying stagnant.

 

[Baked]

My average cruising speed is 75 to 80 on the highway, and 45 to 50 on local (sometimes 60 when nobody's around).

 

[Red Storm]

You can't change the laws of physics. Gas mileage drops off above 55 because of air resistance. Cars are always becoming more aerodynamic but there's only so much you can do.

Well then my car is breaking the laws of physics. I get better gas mileage going 70 than I do 55.

 

[surfsatwerk]

Bring back prohibition!