Price of gas getting you down? Drive SLOWER!!! (NSFW)

[hutash]

I don't think anyone here inferred that it is a linear function. In fact, in my original post, I stated:

" But of course it's NOT linear...as efficiency is being countered by ever increasing air resistence."

--

Ahhh, but what if the car was on a treadmill?

BTW- none of the cars pictures are Jeep Liberty's.

[Mazderati]

[Tippster]

Ahhh, but what if the car was on a treadmill?

BTW- none of the cars pictures are Jeep Liberty's.

Naked chix don't wash Jeep Libertys; CJs maybe.

[wooley12]

Interesting thread to read given I had a 70k mile/year sales job when the 55 mph max was in effect and you could only buy gas every other day. Semi drafting was a valuable business skill. Which brings to mind the time I put a full sized van up on 2 wheels at 55 mph from following a semi too close when a skid fell off. That was a rush!!

Actually, much more would be saved if drivers didn't act like it was the last corner on the last lap of the Daytona 500 every time the light went green.

[MontuckyFried]

Actually, much more would be saved if drivers didn't act like it was the last corner on the last lap of the Daytona 500 every time the light went green.

Exactly! Even in a 4-cylinder econocar, that style of driving eats up WAY more gas than my "thirsty" V-8 does, especially since like 99% of my car's miles are on the highway. If you have a problem with people's gas consumption, don't just blame the speed limits (still too low IMO) and aerodynamics...also blame bad driving habits like jack rabbit starts at green lights, or people not changing their air filters, or not properly maintaining their car, or using the wrong grade gas, or...

[TomCrac]

Is the debate over that 55 saves lives?

What about picking up speed on the downhill to ease over the uphill?

I drafted a tour bus on the way home from the hill the other day ... For almost 2 hours .... Amazing how much gas I did not use, the needle hardly moved.

[Crock]

Ahhh, but what if the car was on a treadmill?

Depends. Are the headlights on or off in this scenario?

[DJSapp]

good thing we are getting rid of the EPA!!!

No, my point was moreover that the EPA test is outdated, and auto manufacturers design transmissions to perform on that test. There is no reason that my new 365 hp truck needs to hold 2100 rpm to maintain 70 mph. Seriously, a max speed of 60? You would be run off the road by a school bus in CA for going that slow.

And yes, air resistance increases exponentially with speed. However, when you change the gearing in the car to aim for a different sweet spot (i.e. GREATER THAN 55), you can actually improve the overall fuel economy (fuel economy is a ratio, not a direct measurement of anything). Motors are more powerful than any other point in history, but we can't take advantage of gearing to improve the fuel economy since the test hasn't been updated to reflect these improvements.

Proof? Ever feel like you need to constantly feather the gas pedal to maintain a speed? That because your car doesn't want to hold that speed. Motors perform most efficiently at a constant rpm, and auto makers typically gear cars to be near the bottom of the gear range for typical speed limits. 25, 40 and 55. Pay attention to that the next time you drive to work.

Nerdy proof: you need approximately 100 hp to overcome drag at 70 mph in a truck (0.6 coefficient, 26.5 sqft area). How do you gear a 350 hp motor to put out 100 hp at 70 mph with as few rpm's as possible? I'm not a mechanical eng, but it doesn't seem that tough to optimize gearing for using 29% of peak power...

[theshredder]

Its cubic, not exponential.

Considering only wind resistance and not mechanical efficiency issues will not explain the mileage window.

At constant speed, I think the lower the RPMs, the better the efficiecy. Taking into account drag, the lowest gear and lowest RPMs possible is the most fuel efficient way to get around. But slow. I'd be surprised if 5th was more fuel efficient than 4th at the same RPMSs.

I once estimated that about 10 or 20% of the total kinetic energy in the old car was in the rims and tires spinning (neglecting other spinning parts, and assuming discs for wheels). That could add up in the city.

Edit: Ahh it depends on throttle too. If you have to give it tonnes of gas to get up hills at low RPMs that might have an overall negative effect. I don't know.

[Alaskan Rover]

Time is money AK. 20 miles per hour less = 20 minutes per hour wasted. What's your time worth? How much would that lower the productivity of America. We're supposed to do things to HELP the economy AK. Not wreck it even more for some psycho religion called enviromentalism.

Ah....and thereupon lies the crux of this economic impasse we've got going on Capitol Hill presently!

The conservatives think time is money.

No!! Only time can be time. In fact, I'm not even sure if time is time. But I DO know that it is certainly not money. Any kindergartener will tell you that's silly.

Is money even money? Is credit money....or just some masquerading fraud? Some two-faced tart that will gladly steal your wallet after a night of mediocre sex?

If time is money, does that mean money is time? I've got a bunch of change and maybe 3 crumpled dollars in my pocket that went through the wash.....can I then exchange those for time?

I think if money was time, you'd have a whole bunch of VERY ancient billionaires around, wouldn't you?

Just some pre-coffee thoughts before morning focuses itself its cold beams on me.

--



If ti

[skiballs]

AR in person

[nick > jesus]

Get a more efficient and aerodynamic car. On a recent trip I was getting 31 at 90 and 34 at 80 in a vw cc.

[splat]

A picture is worth a thousand words.....big hint in small type

[DaveTV]

OR we could drive cars that don't have the aerodynamics of a brick.

My Mercedes E350 4matic wagon gets better gas mileage at 75/80 than at 55.

Whoa, I never heard of this, is this documented by others as well..?? I would like to see it..

[jfost]

No, my point was moreover that the EPA test is outdated, and auto manufacturers design transmissions to perform on that test. There is no reason that my new 365 hp truck needs to hold 2100 rpm to maintain 70 mph. Seriously, a max speed of 60? You would be run off the road by a school bus in CA for going that slow. ...

I know, and I agree with you - the EPA comment thing was for DbT...

[MontuckyFried]

Hey OP, where do you live? Because when it comes to mpg, something to consider is what terrain you're dealing with. Whenever I'd drive around Colorado (especially that I-70 drive from Denver to Summit County), my 5.7 liter Caddy got better gas mileage than my 2.3 liter Mazda. Being up at altitude, combined with the climbing, my Mazda was gasping for air, and I'd have to keep the pedal pegged to the floor to keep up with traffic. Maybe it's because the ECU was used to lower altitude driving (got a check engine light a couple times above 10,000'). The Caddy in contrast, was able to cruise in 6th no problem, and didn't even seem to care how high or steep we were.

SO it would appear that if you're in the mountains, a higher powered car, whether by displacement or turbo-charging can be more efficient than some puny car. Also FWIW, my buddy was behind me in a Prius. The first major climb completely drained his battery, and by the time we got to our destination, his mpg average had dropped to the mid 20's. Hmmmm. About the same as my CTS up there! And I was having WAY more fun than he was. That Prius was not having fun on those climbs once that battery was gone. He ended up about 10 minutes behind me.

[uglymoney]

I remember trips across Nebraska when the limit was 55. It was PURE TORTURE and it took hours longer to get to Denver than it does today. You'd have to get a hotel room in the middle of nowhere because it took so long. Cops were everywhere pulling people over. I'm all about saving fuel to the point that we're seriously considering buying a Prius or some other little ultra efficient or even electric clunker but that law was the dumbest law ever.

[uglymoney]

My 2.5L Subaru always gets better mileage in the mountains that in the plains. And that includes a car full of gear and people and me flogging the shit out of it over passes. We get like 29 regularly out there but I almost never see that around here.

Another note is that you will always get better mileage in the highest gear possible at full throttle than if you shift down and use part throttle. This is super easy to see on fuel computers.

[MakersTeleMark]

Another note is that you will always get better mileage in the highest gear possible at full throttle than if you shift down and use part throttle. This is super easy to see on fuel computers.

80 mph. 80 mph. Oh wait, RPM's, what does that mean?

[doughboyshredder]

Time is money AK. 20 miles per hour less = 20 minutes per hour wasted. What's your time worth? How much would that lower the productivity of America. We're supposed to do things to HELP the economy AK. Not wreck it even more for some psycho religion called enviromentalism.

My guess is 9.00 an hour on a good day.

Akr is a great example of a common problem with people. They think they figure something out and decide to force it on others. For liberals its speed limits, for conservatives its what you do in the bedroom. Fucking reeediculous.

My time is billed at 65-100 an hour. I have no problem paying for a bit more gas and the occasional lawyer fee to keep my speed around 75-80. If you want to do 55 help yourself. Just do it in the right lane.
Sent from my PantechP8000 using TGR Forums

[doughboyshredder]

Ah....and thereupon lies the crux of this economic impasse we've got going on Capitol Hill presently!

The conservatives think time is money.

No!! Only time can be time. In fact, I'm not even sure if time is time. But I DO know that it is certainly not money. Any kindergartener will tell you that's silly.

Is money even money? Is credit money....or just some masquerading fraud? Some two-faced tart that will gladly steal your wallet after a night of mediocre sex?

If time is money, does that mean money is time? I've got a bunch of change and maybe 3 crumpled dollars in my pocket that went through the wash.....can I then exchange those for time?

I think if money was time, you'd have a whole bunch of VERY ancient billionaires around, wouldn't you?

Just some pre-coffee thoughts before morning focuses itself its cold beams on me.

--



If ti

Written like a true dishwasher.

Disputing that time is money only proves my theory that your skillset places you squarely in the burger flipper dishwasher group.



Sent from my PantechP8000 using TGR Forums

[Mofro261]

take it easy.

[Flexon Phil]

Diesels. We need more better options in motors.

[uglymoney]

80 mph. 80 mph. Oh wait, RPM's, what does that mean?

I'm not sure what you mean but I was talking about climbing hills not flogging it on flat roads for fuel economy. I guess I neglected to mention that thinking it was obvious but it wasn't.

[Alaskan Rover]

Hey OP, where do you live? Because when it comes to mpg, something to consider is what terrain you're dealing with. Whenever I'd drive around Colorado (especially that I-70 drive from Denver to Summit County), my 5.7 liter Caddy got better gas mileage than my 2.3 liter Mazda. Being up at altitude, combined with the climbing, my Mazda was gasping for air, and I'd have to keep the pedal pegged to the floor to keep up with traffic. Maybe it's because the ECU was used to lower altitude driving (got a check engine light a couple times above 10,000'). The Caddy in contrast, was able to cruise in 6th no problem, and didn't even seem to care how high or steep we were.

SO it would appear that if you're in the mountains, a higher powered car, whether by displacement or turbo-charging can be more efficient than some puny car. Also FWIW, my buddy was behind me in a Prius. The first major climb completely drained his battery, and by the time we got to our destination, his mpg average had dropped to the mid 20's. Hmmmm. About the same as my CTS up there! And I was having WAY more fun than he was. That Prius was not having fun on those climbs once that battery was gone. He ended up about 10 minutes behind me.

My original post was not based so much on where I live, but what I see when I'm traveling elsewhere. Where I live fuel efficiency basically goes right out the window....lots of mountain passes, lots of twisting turns and lots of long hills.....and no interstates. The hills basically mean a coping mechanism of accelerating downhill to get enough momentum to get to the top of the next small hill, much as you describe.....and then the passes are just a long, slow "chilkat-trail" uphill slog, followed by the downhill where you can coast for sometimes MILES.

In this thread, I'm talking about what I see when traveling on lower 48 interstates, instead.

The average speed of interstate travel has gone way up, in general. I think mostly our society in general has speeded up. We can literally get ANY information about ANYTHING right on our always present smartphone, INSTANTANEOUS. I think our highway speeds just reflect this new "higher speed society". I guess I sorta "tilt" at the 'windmills" of this new 'everything NOW" society even while being a user of high-tech myself.

But I find difficult to grasp that people nowadays just categorically dispatch with notions of driving slower as some anachronic notion. It's not. Most of the cars doing 80 on the interstate WOULD save fuel if they drive slower. It's simply a factor of air resistance. Tippster...your Mercedes wagon would get even better mileage if you drive at 60....that's all I'm saying. If we could magically invert the laws of physics so that air resistance goes down as speed goes up, I'd have little problem with high highway speeds....as I'd be using those same inverted laws of nature to take wing like a bird.

Because few would voluntarily slow down on the interstates, and because just one or two cars driving 25 mph slower than average traffic may be unsafe, the ONLY way to get highway speeds down would be to lower the interstate speed limit to say 60 and in places 65...and ENFORCE those new limits.

One way to enforce even the speed limits we have now, would be to let many of the LEOs drive their own vehicles while on speed limit detail...give them stipends to pay for fuel and wear/tear on their vehicles, equip them with lights in the grill, and taillight strobes....IF said officer drives a fairly new, fairly quick car. For arrests and DUIs and such, the officer would of course course call for regular squad car back-up. At the same time, have many more official unmarked cars for traffic detail that AREN'T so damned obvious!!

People would give speeding VERY much of a second thought when they don't know if the ordinary car behind them is actually a cop!!! This would work better than anything now.

--