Why cars aren't getting any better mileage and maybe even worse..

[Fumesucker]

I've been watching the NOVA special on "the car of the future"...

A direct quote from the first chapter of the show: "Since 1985 average vehicle weight has increased by 1000 pounds"..

There you have it, heavier vehicles require more energy to accelerate them and take them up hills.

So even with increasing efficiency in the engines (which they really are), the overall efficiency drops because the cars are heavier.

http://www.pbs.org/wgbh/nova/car/program.html

[Warpy]

1. Right, and that's why I get as few tchotchkes as I can get away with

My Korean econocar is a manual with power nothing. It does have AC, a necessity here in the desert, but that's it. I adjust my own seats, open my doors, and crank my windows down.

It got 40+ MPG on a 300 mile trip last fall with the AC on for part of the trip.

[Javaman]

53. I know what you mean, I just had to pass on the lead tires on my new car. ;)

LOL

cheers.

[elehhhhna]

2. That doesn't even begin to address the increasing weight of the PASSENGERS.

I truly b'lieve SUV's are popular b/c they're easier for the obese average American to get into & out of.

[Fumesucker]

3. Perhaps....

But I know that a lot of people find being up higher to feel safer, whether or not it is really so.

The first really tiny car I ever had was 1962 Lotus Elite back in about 1971.. I could look out the driver's window at a VW Beetle and be looking right at the Beetle's door. It took some getting used to to be that low..

FWIW, that little Lotus would haul ass with a 1000 cc engine..

[Missy Vixen]

8. I have a 1994 Nissan Sentra

>I truly b'lieve SUV's are popular b/c they're easier for the obese average American to get into & out of.<

My husband drives a 1996 Toyota Tacoma. We're both fat. That kind of messes up your SUV "evidence", doesn't it? I might also add that those we see still driving SUV's and Hummers all seem to have children. We don't.

Julie

[Javaman]

54. New from Lotus the Wideus...

Think about it...

[slor]

60. LOL...you made me laugh...

it may be mean, but I needed a laugh after my day.

[JustABozoOnThisBus]

66. BS!!! It's my belts that have shrunk over the years!!!

:rofl:

[Fumesucker]

4. Another direct quote..

AMORY LOVINS: We started digging into how to make the car lighter, with better aerodynamics, with lower rolling resistance. We ended up concluding it was quite straightforward to triple the efficiency of a car, at roughly the same cost.

[DJ13]

5. I was getting over 38mpg (hwy) in my 1984 Civic

Outside of their hybrid, almost no Honda made 23 years later gets as much.

[Fumesucker]

6. The first Civcs weighed 1500 lbs..

And could get 40 mpg hwy.. in 1973

The latest Civics weigh about 2600 lbs..

And don't do as well on gas despite 35 years of technology development..

http://en.wikipedia.org/wiki/Honda_Civic

[krispos42]

7. Because more efficiency allowed more power for the same mileage

In other words, once a manufacturer's fleet met the CAFE standards, they applied new technology or expanced existing technology throughout their fleets. They upgraded existing engines (GM's 3800-series V-6 and Ford's 3.8L V-6 and 5.0L V-8, both of which date back some 4 decades) and introduced new engines. Distrubutorless ignition, multiport fuel injection, more computer control, variable-valve timing, overhead cams, tighter tolerences, and 4-valves-per-cylinder technology squeezed more power per cubic inch of displacement and more power per gallon of fuel.

Back in 1988, the Ford Taurus with the base 3.0L V-6 had a 140-horsepower and got, adjusted according to the new 2008 EPA estimates, 21 mpg combined. Now the 2008 Ford Fusion has a 2.3L I-4 with 160 horsepower and gets 24 mpg combined.

So the new car has 20 extra horsepower AND gets 15% more fuel economy.




And if you look at the optional engine for the Fusion, the new 3.0L 24-valve V-6 with 221 horsepower, it gets 21 mpg combined.

So a difference of 20 years means that, for the same fuel economy, you get 58% more horsepower.


Now, if we were to limit ourselves to 80's-era horsepower, we would be seeing compact cars like the Chevy Colbalt, Ford Focus, Honda Civic, and Toyota Corolla with between 60 and 100 horsepower.

The 1984-1987 Honda Civic, for example, had 60 hp base and 76hp optional. The Ford Escort of the same era had 86hp.

[LondonReign2]

9. Only drive downhill

Then the added weight will work in your favor. Or does that violate Newtonian physics?

[LondonReign2]

10. Only drive downhill

Then the added weight will work in your favor. Or does that violate Newtonian physics?

[aint_no_life_nowhere]

11. I knew a guy who lightened a Honda CRX

It's a small, light and efficient two-passenger car to begin with. But this guy did it as an experiment. He removed the windows and used high-strength but lightweight Lexan plastic (there apparently was a kit for it). He removed the hood and replaced it with plastic composite (also a racing kit). He removed the gas tank and put in a lightweight plastic gas tank. He removed the seats and put in ultra lightweight racing seats (also an available kit). He put a lightweight but expensive lithium battery in place of the lead acid one and saved about 12 pounds on that. He drilled holes in internal parts like the dashboard and plugged them up with plastic putty and repainted it. He did other things that I don't recall. He said he eliminated almost 300 pounds from the lightweight car and according to him the mileage significantly improved in a car that already had great gas mileage and pep. If there were a way to easily hybridize such a car, I'll bet he's trying that too.

[Fumesucker]

12. Even more effective ..

An under car shroud to smooth the underside of the car for increased aerodynamic efficiency and a lower drag coefficient.

Rough surfaces increase drag and decrease efficiency, the air doesn't care which side of the car it is on, the underside of the car should be as smooth as possible.

[aint_no_life_nowhere]

15. Good point

I recall that he mentioned something about that. Guys who race these CRXs have several racing kits available to make these modifications, but he wasn't doing this for racing purposes, but to see how efficient he could make the car. He also said he was going to strip off all of the undercoating from the car which supposedly weighs a couple dozen pounds. In southern California where it seldom rains and never snows, it shouldn't be that big a deal.

[lectrobyte]

30. A hybridized CRX? Honda did that already, called the Insight...

I miss my '90 CRX. It was a DX, not the high-MPG HF version, but I could drive the be-jebus out of it and still get in the high 30's.

[alfredo]

13. Ethanol also decreases mileage.

[Fumesucker]

14. That's because ethanol provides less energy per unit volume

Than gasoline..

Not to mention that an engine optimized to run at maximum efficiency on pure ethanol would not be suitable for running on gasoline, the compression ratio would be far too high. Pure ethanol has an octane rating of 110 or higher..

http://en.wikipedia.org/wiki/Octane_rating

[alfredo]

21. It a win win situation, less mileage per gallon, higher prices.

[hfojvt]

17. Really? I could have sworn I got better mileage with ethanol

I never documented it, but always kept running averages in my head and consistently did better with gasohol.

[Fumesucker]

20. Yes...

http://en.wikipedia.org/wiki/Energy_density

[truedelphi]

42. I think ethanol was touted as being good for gas mileage

And then there are other factors - getting your car tuned up can increase MPG...
also having your tires inflated to the industry standard.

And if it is windy one day and not windy another, your gas mileage will vary. Going against a heavy wind can greatly decrese the gas mileage and going with the wind can increase it.

[Pavulon]

23. It also disrupts petro states

by pricing oil at the $100 a bbl mark they make bio products and plug in hybrids viable. Hopefully these will allow redirection of trillions of dollars we pay to assholes to stay in the states. I would rather pay ADM and the power companies. At least they are not spending the money we pay them to try and kill us.

Ethanol is home grown and well worth the trouble. Hydrogen and electric is better.

[alfredo]

27. Much of our diet is corn based whether you know it or not. More corn based

ethanol, the less corn for food. Less corn for food, means more stress on wheat and other grains.

[krispos42]

36. Yeah, but we can feed the corn waste to the cows

And eat the cows. Because, remember, if a cow could eat you, it would. :-)


We also need wind-powered ethanol plants. Plenty of wind and corn in the Midwest, so combine them! Stop using natural gas to distill it.

[alfredo]

50. You need to read Michael Pollan's book "In Defense of Food."

We eat too much corn or corn derivatives.

http://www.michaelpollan.com/

[Fumesucker]

29. The net energy gain from ethanol

Is only on the order of about 20%, it takes a lot of energy to grow corn, plowing the fields, chemical fertilizer, transporting the corn to the processing plant, etc, etc..

Switchgrass or hemp would be much more suitable for biofuel production..

[Fumesucker]

45. You do know that the single biggest foreign source of oil for the US

Is Canada?

Right?

[krispos42]

51. Yup. But by sucking up so much oil...

We're enabling the market for Middle Eastern oil. If we're sucking upo Canadian and Mexican oil, other countries have to use the MidEast for their oil.

[CRF450]

16. Thats right! The engines are getting more effecient...

Even the 7.0 505hp v8 in the Corvette can get up to 30mpg HWY because the car itself is 3200lbs, very aerodynamic, and the 6 speed transmission has very tall gears! This is a good video of the base Corvette with the 400hp LS2, showing both the acceleration and mpg readout. http://www.youtube.com/watch?v=q7j51CAKh3Q If you look when the driver was slowing down, the mpg meter was jumping up near 60mpg, but when he set the cruise at 60mph, it was getting 31mpg.

Cars would be doing alot better if they werent so damn heavy now.

[CRF450]

18. Heres another video

http://www.youtube.com/watch?v=DO3Qt20DFUg&feature=related

[ColbertWatcher]

19. What about speed limit?

I know I waste more gas going 65+ than when the speed limit was 55mph.

And the car is not as efficient.

Anybody remember the story about why and when the speed limit was changed?

[Fumesucker]

22. That's not really germane to the discussion..

And not all cars have lower mileage at 65 than 55, it has a lot to do with the torque and efficiency curve of the engine and how the car is geared.

There is a characteristic of internal combustion engines called brake specific fuel consumption (BSFC), basically it measures how much fuel it takes to make one horsepower. This characteristic varies according to a lot of variables and one of those variables is engine rpm, if the rpm is too low BSFC falls, it takes more fuel to make one horsepower than it does at higher rpms. Also if the rpm is too high BSFC falls, engine friction climbs quickly with rpm..

My daughter has a 97 Expedition with the 5.4 OHC engine and a MPG readout.. There is literally no difference in fuel efficiency between 55 mph and 65 mph, this is because at 55 mph the engine is turning too slowly to be in an efficient portion of the BSFC curve.

[ColbertWatcher]

24. Efficiency is no different, but...

...don't you use more gas at 65 mph than at 55?

[Fumesucker]

25. As I pointed out..

It depends on a great number of variables..

My daughter's Expedition gets a lot better mileage at 65 mph than it does at a steady 35 mph..

If the car is designed for maximum economy at 65 mph, it could well get worse mileage at 55 mph.

Yes, it takes more energy to travel at 65 than 55, the air resistance is higher.. But there are a great number of other factors to take into consideration.

If you had two otherwise identical cars, one of which was optimized for 55 mph and the other for 65 mph then the 55 mph car would get better mileage at 55 mph than the 65 mph car at 65.. But that is not the case, most cars are optimized for more like 65 to 70 mph cruise since that is the speed most people drive.

[ColbertWatcher]

26. What I meant was...

...don't you use more gasoline overall--not just efficiency-wise--but overall number of gallons used going 65 than going 55?

[Fumesucker]

28. Not necessarily..

If you get the same miles per gallon at 65 mph as at 55 mph then you use no more gas to go the same distance..

That's what miles per gallon means.. How many miles you can go on a gallon of gas.

My daughter's 5.4 Expedition gets 22 mpg at 65 mph and 22 mpg at 55 mph..

What really shocks most people is that it gets about 17 mpg at 35 mph, it even surprised me when I found that out but I finally figured out that the overdrive transmission doesn't kick in until 46 mph so it's like driving around in a lower gear.

[Mnemosyne]

37. Questions re: use of overdrive.

When should overdrive be used?

What if it stays on?

What exactly is it made to do?

I used to help restore the bodies of vintage and antique cars and trucks for a living, but the mechanical/ electrical, etc., has always created a horrid brain block for some reason.

I cannot ever remember if you check the tranny fluid when the engine is cold. Or is it the oil? :banghead:

I stand completely in awe of those that can work out the complexities of engines specs, ratios and more. My ex could tear anything apart, engineer any part to suit him and have pretty decent results the first time usually!

But I can design and build a decent kitty coop out of chicken wire, old boards, cheap garden arch parts and those plastic handcuff type ties, fairly easily. :rofl:


Thanks for sharing your knowledge on these things. :hi:

[CRF450]

39. Answers for OD

OD is basically the final gear plus the torq converter locking. When should it be used? Why turn it off? It'll shift into OD when the vehicle is going fast enough, it will go slower in the final gear, but the torq converter wont lock till your going a little faster. OD only helps fuel milage at higher speeds usually faster than 45mph, turning it off will give you worse fuel milage at higher speeds, and it will makes no difference at lower speeds cause it not going fast enough in the first place.

I'v seen people mistake their 4 speed auto as being a 5 speed, cause as its shifting through the gears, you'd see it shift four times, and then one last time. That last dip in the rpm's is the torq converter locking.

[Mnemosyne]

49. Thanks, CRF! between you and Fume, it is much clearer now.

:hi:

[Fumesucker]

40. Overdrive is designed to lower the rpm of the engine at cruise speeds.

With modern overdrives on automatic transmissions, just about the only time you should turn it off is if you are towing a heavy load or perhaps descending a very steep and long grade where you might overheat the brakes if you use them to slow you down.

Even towing a heavy load, leaving the overdrive on won't hurt anything, it will just be a bit annoying as it kicks in and out going up and down hills.. You will see and feel the engine rpm rise and lower in jumps as the OD cuts in going downhill and out going on the flat or uphill..

Overdrive is basically just another gear in the transmission.. Most of the time these days it is also combined with a lockup torque converter.. Torque converters normally have a little bit of "slip" in them, this is what allows an automatic transmission to remain in drive with the engine idling and the car sitting still.. This "slip" wastes energy though so some torque converters have a mechanism which locks out the "slip" at higher speeds..

Overdrives have actually been around for a long time, since before automatic transmissions were invented I think.. Some of the six speed manual transmissions in the newer cars are actually a five speed with an overdrive sixth.. For all practical purposes you can just think of it as one more gear in the transmission.

The practical effect of an overdrive is to increase gas mileage at relatively high cruise speeds by lowering engine rpm..

On most cars you check the tranny fluid when the engine is hot.. with the oil it really doesn't matter that much, cold or hot is fine.

[Mnemosyne]

48. Thanks, Fume! You have a great way of simplfying it.

I am going to write down the tranny and oil info and put it in the glove box.

Thanks again! :yourock::hi:

[ColbertWatcher]

64. So...

...why do I hear all these reports of truckers driving slower?

Why do they think they'll get better gas mileage at a lower rate of speed?

[NickB79]

61. You are ignoring the increased drag associated with higher speeds

One widely-quoted number I see mentioned (such as on Car Talk on NPR), is that the average car's drag doubles when you go from 50 mph to 75 mph. I'd suspect that one of the reasons your daughter's SUV has no difference in mpg at various speeds is that, aerodynamically, it's a brick on wheels.

I drive a Scion xA, a subcompact that's rated at 38 mpg highway. Most of my extended family lives 120 miles away, almost all highway driving, and I've noticed that when I drive 70 mph, I get the stated EPA mileage. If I reduce my speed to 60-65 mph, I get a tad over 40 mpg. Once, late at night when the roads were empty, I set my cruise to 53 mph and got 48 mpg!

[CRF450]

62. The xA isn't that much of an aerodynamic car either.

Plus its has a 4cyl with not much torq at all. When you have a car like a Corvette, which aerodynamically it can still easily cut through the air at 75mph, plus a powerful torqy engine, theirs not much difference in fuel economy between 55 and 65mph.

[Fumesucker]

63. I already pointed out several times

That there are a great many factors involved in vehicle efficiency.

I've also stipulated that aerodynamic drag increases rapidly with speed, that doesn't change whether the car is low drag to start with or not.

But the fact remains that cars are heavier on the average by 1000 lbs than they were in 1985.

That's a weight increase of probably around 25 to 30 percent.. A very large difference.

[CRF450]

34. From my observaiton, it seems that lower powered cars get more mpg at 55mph

While the ones with more powerful/torqy engines are geared taller, so the fuel milage can remain mostly the same at higher speeds. Its like a car with a 4cyl at 65mph is running 2500rpm, while the v8 would be running 1000rpm less. Now, alot of cars are coming with 5-6 speed auto trannies instead of the usual 4 speed which somewhat killed fuel economy.

[Fumesucker]

35. Engine friction rises very quickly with rpm

Back in the mid 80's BMW built a series of cars designed for maximum efficiency, the eta series.. 325e and 528e..

Both of these cars had a *bigger* engine turning lower rpm to increase efficiency..

A 325i had a 2.5 L inline 6 with a 6500 rpm redline while the 325e had a 2.7 L inline 6 designed for low rpm torque with a 4800 rpm redline..

The 2.7 engine had fewer camshaft bearing, lower tension piston rings, smaller ports and valves, reduced cam timing and lift and quite a lot of other modifications.. Those cars would get well over 30 mpg at 60 mph and had a lot of torque, they were fun to drive and the final drive ratio had the engine turning at very low rpms at highway speed.

http://video.aol.com/video-detail/bmw-e30-325e-eta-burnout/3930991851

A big engine turning low rpms can be quite efficient because of low engine friction and reduced pumping losses thanks to higher intake manifold absolute pressure (less vacuum).

[BigDaddy44]

31. Cars are safer

They're heavier because we've added air bags, additional support beams, antilock brakes, and other safety measures. These all add weight.

[Blue_Tires]

32. not to mention

the added electronic wizardry (especially in the german cars), and the fact that high performance has been back in style for several years now...bigger engines are heavier engines, and increased horsepower requires heavy-duty components in the drivetrain (transmission, etc)...but ultimately the automakers have not done that good a job of at least trying to keep the weight manageable

of course, i have to mention the crazy increases in these jumbo wheel sizes...when i was in college 10+ years ago, i read all the tuner mags and at that time, 18 inches was considered a HUGE wheel, 19 was like the max you could get on a car, and 20 was the max on SUVs, iirc...now you can order cars straight from the factory with 20+ inch wheels...

[Fumesucker]

33. Mostly they're heavier because

They're bigger..

Right offhand I can't think of any car line that has ever gotten smaller..

Air bags don't weigh much, neither does ABS.. Support beams perhaps but most of the increased safety comes from better design.

A car that is *too* strong is not as safe because it subjects the passengers to higher G forces in a crash, safer cars are designed to crush controllably, this limits the maximum G forces in a crash.

Formula One cars and Indy cars are extremely light and it is not uncommon at all to see the driver walk away after a 175 mph plus crash.

[Blue_Tires]

55. no one is saying a light car can't be safe...

but the lightweight technology that goes into the average open-wheel racer is far too expensive and complex to incorporate into a road car...people want luxury, amenities, premium sound, and room for passengers and/or stuff...you can't even order a bare-bones no-option car from the dealer anymore; because so many options are standard now...but maybe the tide will turn in the near future -- you're not the only one shaking his head over the growing porkiness of all cars, from economy to performance to luxury...

[Fumesucker]

57. If you watch the program I linked to..

You will find that a very lightweight and yet safe, efficient and roomy car can indeed be built for about the same cost as current vehicles.

[Onlydem]

38. replying to why cars are't getting better fuel mileage

Unless they install hydrogen generators then they can get better fuel mileage. I know of several people here in town that have hydrogen generators on their cars and even trucks and get fairly good mileage. A three quarter ton Dodge Ram diesel pick up gets 30 miles to the gallon using a hydrogen generator.
A 4 cylinder Toyota Celica gets 4o miles to the gallon. A Toyota for wheel drive 4 cylinder half ton pick up gets 33 miles to the gallon. A 2005 Buck V6 gets 40 miles to the gallon using the hydrogen generator. Detroit could install them in new cars if they wanted to but the don't because they probably get kick backs from the oil companies. What other reason could there be?

[Fumesucker]

43. What exactly is

A "hydrogen generator"?

[lumberjack_jeff]

41. The 1908 Model T got 25 mpg.

http://www.wanttoknow.info/050711carmileageaveragempg

[Fumesucker]

44. The Model T was quite light..

And generally drove about 25 mph or considerably less.

Roads sucked big time back then, extremely few were paved.

[mucifer]

46. The prius is fairly big (about the size of a camry) and gets

46 mpg combined city and hwy and it has a huge heavy battery.
.

[Fumesucker]

47. Curb weight on a Prius is about 2800 lbs..

Curb weight on a non hybrid Camry is about 3400 lbs.. The hybrid Camry weighs almost 3700..

The two cars are not comparable in size..

http://en.wikipedia.org/wiki/Toyota_Prius

http://autos.yahoo.com/toyota_camry_hybrid_4_door_sedan-specs/?p=ext

Not to mention that a Prius has a 78 horsepower engine optimized for efficiency..

[aint_no_life_nowhere]

56. Wow - that's heavier than a 1968 Mustang

The 1968 Mustang with the 6 cylinder 200 cubic inch engine was about 2659 curb weight. The 289 model was slightly heavier. I would have thought that use of high-tech materials such as high-strength, lightweight kevlar-resin composites and unibody construction could have been used by now in autobody construction to bring the weight down. I'm frankly astounded by your post and the current weight of cars, including supposedly more high-tech fuel-efficient cars. I wonder if the added weight has something to do with increasingly stringent crash resistent vehicles. But that may not make sense, because one of the greatest crash resistent commercial cars ever built was the Citroen DS, built back in the 1960s. Guys could drive it into a concrete column at 60 mph and walk away. The entire car was built to fold up and the engine slides right under the passenger compartment. Even the steering wheel is designed to "give" and bend so that it doesn't hurt the driver in an impact. And the Citroen wasn't that heavy (2800 lbs. curb weight). Citroen was the pioneer in unibody construction (the Traction Avant being the first mass-produced unibody construction car in the 1930s).

[Fumesucker]

58. LOL.. Citroen DS

A friend of mine's dad had one back when I was in high school in the sixties..

It had the adjustable height suspension with a lever on the dash that would make the entire car go up and down..

We used to pull up next to someone at a red light and then wave at them while the car went up and down.. Left a bunch of people scratching their heads over that..

I don't remember what movie it was but I remember a scene where a DS got cut in half right behind the rear seats and still continues the car chase with only the front half of the car still there.. I laughed my ass off..

[riverdeep]

52. I saw the start of this program and had to leave at about fifteen minutes in.

Thanks for reminding me of this. I love Click and Clack. And I'm not even into cars. One thing I recall them mentioning is that cars were marketed for bigger is better and more powerful is good. I don't think you need too much marketing savvy to do that, anyway. Most Americans, especially in the 90's when the good times would never end, already are primed for this. In cars, in houses, in restaurant meals- supersize it!

Personally, I laugh at the snippets of car commercials I see. Flying down a curving road at 75 mph? Right! More like sitting in stop and go traffic. 0 to 60 in 4 seconds? Great, the guy ahead of me can't. Besides, the limit is 55 most places. Where exactly am I going get to use all this power?

[CRF450]

59. Thats the problem when you live in the city.

I live out in the sticks where a cop/sheriff is rarely ever seen, half the time I'm going 75mph down the road lol.

[CRF450]

65. Hey Fumesucker, you should see this!

This guy's getting 35mpg in a Corvette. http://www.ls1tech.com/forums/showthread.php?t=760195&highlight=milage+gas I'm really impressed.