Fuel Economy and Oil Dependency

snakeweasel

I'm surprised I haven't seen this posted, but 55 mph is actually the most fuel-efficient speed possible (counting in 5's, at least).

There is no "most fuel efficient speed" for all cars, every car is different. Every engine has its own sweet spot where it runs its most efficient, every transmission is geared differently, every car has different wind resistance. All these things mean that every car will get their best MPG at different speeds.

stever

Welcome to the forums.

I love driving the Great Basin stretches (not to mention Highway 50, etc.) in your native state. But I think a 55 mph limit would be largely ignored on most of those roads absent heavy police enforcement. Or $8 a gallon gas perhaps.

From fueleconomy.gov:

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.

gagrice

The best mileage we have gotten on my wife's LS400 was on a return trip from Las Vegas. We were driving mostly 85 MPH on Interstate 15. We got 27.2 MPG on that trip. It was a combination of using good Premium gas from Nevada and smooth cruising. We rarely get over 24 MPG on the highway with our CA crap Premium gas. The Lexus sits at 1800 RPM @ 70 MPH. Our usually mixed freeway city mileage is 18 MPG.

snakeweasel

Best mileage I ever gotten was in the UP driving from Mackinaw to Green Bay. No interstates and plenty of time ment that we took it easy and did around 60 MPH constant. Got just over 35 MPG which is 2+MPG better than I normally get in the highway doing between 70-75MPH.

0patience

Re Oregon and their "too-low" speed limits, maybe this is another reason they are thinking of experimenting with a per mile charge on motor vehicles. Their gas tax doesn't generate enough revenue since all their citizens are driving conservatively and saving so much gas.

How I wish that were true.
The real reason Oregon didn't raise the speed limit above 60 mph has to do with Federal highway money. Those states that raised the speed limits above 60 mph got less Federal Highway revenues.
And Oregon is so cheap, they didn't want to lose any money.

Oregon politicians don't care about their citizens. Only what the federal govt will give them.

nippononly

But then.....Oregon has no sales tax, no income tax, so it can be a pretty good place to live, I would imagine. A number of distant relatives of mine have retired to there and have nothing but good things to say about it. Plus, unlike California and Washington state, it is a pretty rare thing indeed to see an Oregon state trooper on the highway. Even though I-5 is posted at 60 in that state, I pretty much always just continue the 70 mph (that I was doing at the CA border) all the way through Oregon, and in 20 years I have never had a ticket there.

My personal mpg best was in my current car, the Echo, on a highway trip, sticking to 65 mph, very little A/C use (it was evening both ways), 49 mpg over about 1300 miles (round trip). With that car's tiny motor, increasing speed only slowly reduces fuel economy, whereas in my old 4Runner, every 5 mph extra over 50 was a solid point off the already pathetic mpg.

kernick

I'm sure similar issues exist for 18-wheelers, planes, jets, trains, boats, and ships. Where is the concern there for vehicles running at optimum speed for mpg? I believe most of those vehicles are looking to make good time, rather than saving a little fuel.

For example a cruise I took out of NYC to the Caribbean the other year makes the run at full-speed in order to get there in decent time. That can't be too efficient.

belvedere65

Say no to 55 MPH. Sixty Five / Seventy is fine!!!

stever

Ah, I think there's a lot of concern for running other vehicles at optimum mpg instead of speed.

Let's take the US airlines - their fuel bill is ~28% of operating costs. So they are cutting idling time on the runway and only using one engine to taxi to the gate. (USA Today). They are also cutting back on the extra fuel they are carrying and a "flight-management computer conserves fuel by continually calculating the optimal flying speed based on a number of dynamic criteria including weight, wind speed and fuel costs." (USA Today)

I bet it's not much different with tugs pulling barges and semis.

snakeweasel

You also have to consider that slowing down to save fuel may cost profit. A semi driver who is paid by the mile can make more money driving 70 than he can at 60. The barge moving down the river may not be there in time for the next shipment if they slow down. The extra profit made by getting some place sooner may offset the additional cost of fuel.

stever

Time is money, sure. But there are all kinds of tugboat efficiency links on the net for gas saving gizmos, scheduling programs and fancy props.

Not too topical, but USA Today keeps coughing up interesting pages today. This one is all the commercial vehicles going to hybrid technology.

Here's a quote from a letter to Landline, the business mag for pro truckers:

"Fuel was $1.70 a gallon when I started. We all know what it is now. The thing I don’t understand is that drivers complain about the price of fuel while driving 75 mph to 80 mph down the interstate.

Being new at this owner-operator thing, I thought I might be missing something. But when I tried slower speeds, progressive shifting, etc. I saw results. Pulling containers is sometimes hard on fuel mileage, but the info worked – better fuel mileage, longer tire life and best of all less stress."

One more from Landline.

loosenut

--it was stupid back then,and would be just as stupid now..
55 ,while certain cars -mostly the old-three speed automatic,got better mileage at 55,while anything made after 86-like fuel injection,lock-up torque converters,four speed auto's,five and six speed overdrive standard transmissions,ect have saved more m.p.g. than 55 did..and i agree-55 is WAY too slow to drive acrost nevada-new mexico,ect..those roads were desined to be driven at 70..my -93 aerostar gets near 25 mpg -with good premium in it..closer to 22 with the cheap stuff,so,i try to keep premium in it when i can,,
we had a judge who got tired of fining people who said they would get run over if they tried to drive the expressway at 55--..he took his own car out there,locked the cruise control at 55,and darn near got run over five or six times in 10 miles..
..he caused an uproar with th highway patrol,when he started fining anyone who came to court charged with 60 in a 50..the fine?? $1.00--one dollar!!
the cops were pissed,then they said they wern't the one who set the speeds-that was the state engineer's job,they just enforced it....eventually they upped the speed on that strech of freeway..

55 is fast enough to kill you,but slow enough to make grandma feel safe..(quote from "gumball rally")

kernick

55 is fast enough to kill you,but slow enough to make grandma feel safe..(quote from "gumball rally")

And if you can't drive 75mph safely take a performance driving class for a weekend, or stay off the interstates, and enjoy the scenery on the side-roads.

euphonium

True, Oregon doesn't have a Sales Tax, BUT they do have a whoppin Income Tax to go along with their Property Tax.

Washingtonians even have to pay Oregon Income Tax when they work in Oregon. Californians and Idahoists pay OIT if employed in OR. Many consider Oregon the Socialist State of the Left Coast due to their taxes.

fintail

And you can't even pump your own gas! It's bizarro-world down there.

I also notice Oregon cars tend to speed at a greater percentage than Washington cars on I5.

nippononly

Oh, Washingtonians are deadly afraid of their state troopers, who I must say are robot-like in their efficiency. I never speed in Washington either.

fintail

I'm not intimidated by the revenue enforcers here. They are usually not secretive in their exploits...it doesn't take long to know where you can speed and where you can't. They cherry pick the inattentive, and I guess that doesn't upset me so much, as a state patrol is there for little else than that and accident work anyway. Most of them give a 10mph leeway too - and when I drive 10 over is usually not possible anyway. It's the county and city police who are the baddies.

Now when the WSP has brain-dead ideas like putting dots on the road to school people about following distance, and said dots waste tens of thousands of dollars and create traffic jams, then I am irked.

sls002

I have found (with my 98 Aurora and 2002 Seville) that cruising @70 would get me about 28-30 MPG on long trips and I could still drive about 650 miles in one day's drive. With my 2007 SRX cruising 70 gets me about 20 MPG. In local driving I usually drive about 60 MPH, because that is about the speed limit anyway, and driving faster does not get you 10 miles away much faster anyhow. Most of my local trips are 10 to 15 miles from home, with some of that distance in a city. The SRX might do somewhat better cruising at 65 or perhaps 60, but with a six speed automatic, the engine is running about 1500 RPM's @60 MPH in sixth gear. Any incline usually puts it into a lower gear at that speed.

stever

Let's assume oil supplies tighten up for some reason making fuel conservation more of a national goal.

Would a nationwide 65 mph speed limit be tolerable (again, assuming some imperative driving the issue besides simple economics.)?

kernick

Would a nationwide 65 mph speed limit be tolerable (again, assuming some imperative driving the issue besides simple economics.)?

Throughout New england and mid-Atlantic states the highest speed limit is 65mph. It is largely ignored. So I don't see that saving a drop of fuel, here; though you might save some in higher states on poor-aerodynamic vehicles.

If you wanted to save fuel though why pick that route? If it was a national imperative, you would save a lot more fuel by banning recreational consumption of fuels. But then everyone who makes a living off tourism would cry. God forbid we ask millions of people not to take the RV out, or not the run the boat at the lake or ocean this year. Why wouldn't we stop builders from putting oil-furnaces in homes first?

Personally I haven't been on a 65 mph road in 1.5 months, so you could set the speed limit at 55 or 65mph and my savings would be 0. I bet driving on 65+mph roads uses about 10% of our fuel as a nation, with most driving occurring in cities, towns and smaller highways. So looking at it that way, I don't see an interstate 55mph limit as having much effect; I think it would sound good - like we're doing something.

We're going around and around with this issue of trying to solve the energy issue and the higher costs. The fact is there is no solution as long as the world's population continues to expand and drive more.

sls002

It would still be fast enough that you could cover a fair distance in a day's drive and would still be more fuel efficient than driving 80 MPH.

sls002

what is needed is a new source of energy.

kernick

And it also must not disturb the environment in anyway, present any sort of danger, or create any form of pollution. This new form of energy must be totally unobtrusive.

Being serious for a moment, I would say we all could do better at using the non-fossil energy sources we have. I have no problem with windmills in Nantucket Sound, or on mountain tops. i can give up the view for energy. If the people of AZ don't mind solar panels all over the Sonoran Desert - put them in. Take a section of Nevada or Death Valley for that matter, and group 25 nuclear plants there. Heck I've seen Yellowstone on Discovery Channel, now lets fill the whole park with geothermal plants.

If we're in such desperate need for energy, I say we give up a few national parks, before we can't get there anyway. Actually not going to the national parks is a great way to save energy. Leave that gas guzzling RV or pull-camper home. Get rid of the tow vehicle!

louiswei

If we're in such desperate need for energy, I say we give up a few national parks, before we can't get there anyway.

AMEN!!

We can't have cake and eat it too.

stever

Ok, for you I'll qualify it as an enforced 65 mph limit. We can add governors to the cars. :shades:

nippononly

You want to give up the national parks to save fuel and/or add power generation? It is dismaying to me in the extreme that anyone would advocate that view. :-(

snakeweasel

Would a nationwide 65 mph speed limit be tolerable

No as the roads and the laws of the roads are the responsibility of the states and the Federal government should have no say in what the states limit the speeds to.

louiswei

Federal government should have no say in what the states limit the speeds to.

Agree.

However, if the federal government is proposing 100 mph speed limit (outside the city limit) then I am willing to put my opinion aside...

:P

nippononly

It wouldn't be a nationwide regulatory speed limit, you understand, but rather the highest statewide speed limit at which the feds would still provide highway funding. So it would be a condition of money-giving, not a regulation imposed from on high.

snakeweasel

No even if it is just a condition for highway funds it is exceeding what the Federal government should be doing. Its the Federal government imposing its will when it has no business doing so. I understand what it is and it is still wrong for the Feds to do it.

stever

I'd be happy with a federalized speed limit. If nothing else, at least when I head to Oregon, I could keep the cruise control unchanged.

People harp on state's rights but when California implements CARB everyone yells for federal intervention.

kernick

Ok, for you I'll qualify it as an enforced 65 mph limit.

Thank you; you're always reasonable. But the point is - the majority of people are comfortable driving faster than 65mph when the road is clear. Therefore 1) it is impossible then for the law to be enforced except on a "sampling" basis, 2) it makes the typical driver feel like a scofflaw, playing cat-and-mouse with radar units, and 3) if we have so many police resources that we can have cops writing speeding tickets to you on the way to work, I'd say we shouldn't be having other crimes occurring, as the police would have arrested all the drug-dealers, protected the banks and 7-11's ...

We need to set our speed limits for what the majority of us drive on a road. If you have a rural highway where the majority is driving 60mph, and the speed limit is 50, set the speed limit for 65mph, so everyone can continue to drive as they are and be legal, with a little wander-room in speed allowed. If people are driving 75-80mph on a 65mph interstate, set the speed limit for 80mph. Keep the semis, buses and other poor-physics vehicles to a lower speed limit.

Traffic enforcement then only targets the really exceptional speed or behavior. Maybe a new police tactic could be 1 of those drone-aircraft which just circle overhead a randomly chosen area, with a camera and a laser? Look for the drunk or the guys racing each other, and leave the commuter alone.

grbeck

louiswei: However, if the federal government is proposing 100 mph speed limit (outside the city limit) then I am willing to put my opinion aside...

I'd still be opposed to it. A 100 mph speed limit wouldn't work in states such as New Jersey or Rhode Island.

Conditions are different in each state, so the speed limits should be set by the state legislature, which is the legislative body closest to all of the people living in that state.

grbeck

steve: People harp on state's rights but when California implements CARB everyone yells for federal intervention.

But those are two entirely different topics, only related because they both involve vehicles.

If one state implements drastically different emissions policies, it opens the door to ALL states doing the same thing, which makes it much more difficult to design and sell products on a national scale.

The Constitution, by leaving the regulation of interstate commerce to the federal government, was clearly written to promote national markets for goods whenever possible, and various U.S. Supreme Court decisions over the years have furthered this interpretation.

The Clean Air Act did allow California to set its own emissions standards, but it has limited states to either choosing the California standards or the federal standards, to ease the burden on manufacturers.

With California's implementation of standards covering carbon dioxide emissions, the question is whether this is a backdoor attempt to regulate fuel economy, which current federal law (CAFE) has reserved for the federal government.

On the other hand, if Texas has a speed limit of 80 mph, and Pennsylvania has a speed limit of 65 mph, and Kansas has a speed limit of 70 mph, the auto manufacturers can still sell one vehicle that is suitable for all three states.

And drivers are expected to pay attention to the clearly posted speed limit signs and adjust their speeds accordingly (or get a radar detector or CB radio if they don't want to drive the speed limit).

gagrice

People harp on state's rights but when California implements CARB everyone yells for federal intervention.

I think you are mistaking state's rights for bureaucracy out of control. I don't remember a vote on whether diesel cars should be allowed to be sold in CA. Or whether ZEV should be mandated. A state that is controlled by two very liberal cities, does not reflect the desires of the state's population. The bulk of the smog reduction in CA, came about as a result of the Federal mandate on unleaded gas. I do not see where CARB has cleaned up the remaining pollution from ships, trains, planes or heavy equipment.

grbeck

...that many of those who are defending California's right to act on its own in regulating carbon dioxide emissions (on the national scene, not on this board) have been against state's rights on virtually every other subject, and have championed continued expansion of federal power. They have championed the broadest possible reading of the Constitution's interstate commerce clause.

So there is plenty of hypocrisy to go around on this one....

Which means everyone will have to look at the merits of the arguments instead of trading charges of hypocrisy.

nippononly

instead of speed limits, we should have speed guidelines. Put up a signs offering a guideline of 65-70 mph on the interstates to appease the feds, and on bright sunny days with maximum visibility, allow speeds up to 85 or 90 without speed enforcement. If we did that, though, we would have have to have day and night guidelines. Visibility at night is worse, and speeds should be lower then. Rain, snow, and fog would lower the limits at which the police would do speed enforcement.

kernick

Visibility at night is worse, and speeds should be lower then. Rain, snow, and fog would lower the limits at which the police would do speed enforcement.

How about digital speed limit signs that are set by radio-signal by the local police?

Or if each car had a little receiver, it could receive a signal using the same technology as digital satellite radio? Actually if this were routed thru the car's ECU, you could have an electronic governor, and no need to have radar patrols. A nice $5,000 fine (or confiscation of auto) & loss of license for tampering with the ECU would greatly discourage that discourage tampering.

Either system could be payed for by the savings of eliminating radar patrols. Though some communities would lose speeding revenue - ah, too bad!

stever

You could keep all the vehicles to certain speed limits with speed governors. It's pretty common technology now, isn't it? I think a few trucking firms limit their trucks to a maximum speed. Stick a few cameras around and the speeders would stick out like a sore thumb. Get the traffic flowing smoothly, and that'll encourage the futuristic self-driving features to hit critical mass faster, and we'll all be able to drink our coffee and chat on the phone while cruising to Dallas in relative safety.

And think of all the "How to Bypass your Lexus Governor" discussions we could have around here.

And not to worry Grbeck - there is plenty of hypocrisy to go around just in my little basement office, even when I think I'm being sincere. Sort of goes with the territory of being human.

[edit] I missed your last post Kernick - how about just having a traffic controller send speed signals to each car. Then we won't have to press the gas pedal at all.

louiswei

A 100 mph speed limit wouldn't work in states such as New Jersey or Rhode Island.

Well, the federal government can propose the highest speed limit possible on all interstate highways, whether to adopt it or not is solely depend on the states. So instead of an enforcement it's more like a recommendation.

To be honest, besides New England area or part of the East, I don't see the problem of setting 100-mph limit everywhere else in the country (again, outside the city limit of course).

louiswei

Uh...I don't think I like the idea of my car can only go 55 mph no matter what. What if I am in an emergency situation that I have to speed up in order to avoid getting into an accident? My car is limited to 142 mph and I intended to keep it that way.

kernick

Uh...I don't think I like the idea of my car can only go 55 mph no matter what.

I agree. I was just stating the relatively inexpensive technology is there - we have XM radio technology, our cars have ECU's, they just need to be tied together with a receiver "boxy-thingy". Then you would have an electronic governor. The police would basically set your governor based on real-time conditions.

Steve - the way to prevent people from tampering with an electronic governor is - make the penalty for doing so, so steep that the normal person is not going to risk it. If the penalty for tampering with it is $250, yeah people might say what the heck. But if you make the penalty $5,000 or loss of license or confiscation of the car, only some real hardcore people will do that.

So if someone is speeding and gets caught, the ECU is examined, and the driver ends up in a world of hurt. And if $5,000 isn't much for someone with a Lambo (or such), confiscate the car.

boaz47

are whole counties I have driven through in some states that would go bankrupt if cars couldn't exceed 55.

I just doubt if anyone would vote for such legislation.

naatz1

I had to go back to page 1 to see what the purpose of this forum was, and was hoping it was to save gas @ 55mph. Anyone with a trip computer in their car can see it does save gas @ 55 vs 65 or 75, whether flat terrain, AC or no AC, windy or not.

But no one will drive that speed unless conditions force them too. And there are plenty of OTR drivers whether truck, shuttles, or just sales and people doing daily long commutes where this would have a serious impact. So unless we had a real serious gas shortage (ie, rationing, $6+/gal, middle east war kinda thing) it's unlikely 55 would work 30 years after the last time we dealt with it.

A better and safer option is sticking with a true 65-70 range to keep the right lane going at one speed and minimize the left lane autobahn blasters. It's insane driving from Chicago to Minneapolis and plenty of other semi-rural locations on 4 lane interstates with zigging and zagging left-right-left to gain a few extra mph. Maybe invent a technical way that the right lane is 65, left is 70 ... I am searching for "non Big Brother" ideas here guys (not sure if it's governors or what) but we can put our cops to better use chasing other hard crimes than adding more to the highways.
And for those that could afford the time to drive 65, you do save some petrol too.

Oh yeah, if we want to save even more gas and help the soon to signed 35mpg average, let's figure out a way to idle down, reduce flow/cylinders, or maybe do an auto off/on hybrid-like shutdown while at stop lights. I would think it could be added to new cars with proper stop light sensors gated by lane direction, allowing for restarts in D gear or whatever with possibly an add-on (similar to the many remote start adders?) for some of the existing fleet. Something to think about for urban commuters, and you just need to have a good battery!

tgkoenigsegg

How about different speed limits depending on traffic and prevaling weather conditions? Every few miles or so could have a dispay above each lane to show which lanes could go the set speed limit.

andres3

The main problem with government controlled speed governors is they could cause accidents and injuries and then you'd have to sue the government. Sometimes you might be going the maximum speed limit and then have an emergency need to briefly accelerate quickly; we'll, the absolute speed governor would prevent that manuever and therefore cause an accident that would otherwise never happen.

Terrible idea.

andres3

Rain, snow, and fog would lower the limits at which the police would do speed enforcement.

Negative. I can confirm that when it is rainy, very cold, or foggy there is zero California Highway Patrol speed enforcment going on. They only like to go on speeding ticket binges when its nice and warm and sunny out.

that happens to coincide with when most of the drivers are "speeding." as defined by the logic-less CA vehicle code.

imidazol97

I can't think of any example where a vehicle going at a governed 65 or 70 mph maximum speed would need to speed up drastically and rapidly to be "safer" rather than _slowing_ down to avoid an accident.

stever

Long before NAVs were common, a client cruising down I5 to Sherman Oaks called me on his cell for driving directions. I was on the speaker phone up in Anchorage for about 15 minutes off and on, using MapQuest at my end to keep him appraised of exits, etc.

After the first five minutes of this, my friend said he was being pulled over and hung up on me. When he called back a few minutes later, he said it had started to rain and a CHP pulled him over to warn him of slick conditions. My friend was doing the speed limit.

Towards the outskirts of LA, he was cruising along (still yakking to me on the cell) and a different CHP pulled him over to warm him to slow down.

We were bemused but those freeways get pretty slippery when wet, especially after a long dry spell.

nippononly

Differential speed enforcement and speed guidelines rather than limits could work, I feel certain!

Maybe anyone getting a ticket should have to get additional in-car driver's training too, like one of those smart driver courses.