Bobvis offers up the point from a book and other sources that we should focus on overall percentage increases in energy efficiency rather than pooh-poohing increases that look small on paper but have larger impact. The test case is a Dodge Durango (12-mpg to 14-mpg versions) versus Honda Civic (33-mpg to 45-mpg versions).

Will counters back the point echoed by a lot of environmentalists, which grates on me, that the “real” disparity is between the 12-mpg Durango and the 45-mpg Civic, and that the goal is to get the Durangos off the road in favor of Civics. In the long haul, I think both sides of the equation are really missing out on very important points that throw off the calculations.

Point #1 – If you’re a single person who never travels far and never carries much, a Civic might work for you. While I think it’s silly for a person who never hauls cargo to have a giant truck, most people need at least some cargo space; I’ve regularly cursed the lack of it in my current vehicle, sometimes for things as relatively minor as IKEA furniture (which is already highly compressed since it’s not already put together).

Ironically, it was the CAFE (Corporate Average Fuel Economy) standards, those listings of what the “average fuel efficiency” (in miles per gallon) of a manufacturer’s fleet had to be, that started some of this inanity. CAFE standards are not universal; you have one category for cars, one for “SUV” class vehicles (aka “light trucks”), and one for honest-to-gosh “Trucks” (usually, but not always, diesel). When CAFE standards were upped, manufacturers had a hard time getting the venerable station wagon (heavier/less aerodynamic than a “normal car” but still classified as one and retaining the car’s lower center of gravity for better handling and less worry of tipovers on curves or in high winds) to fit into the “cars” category, but they could get the minivan (with all the handling, high center of gravity, and aerodynamic efficiency of a rolling brick) to easily fit in while classified technically as a “light truck”.

The result? Station Wagons, which usually averaged 21-23 mpg, were replaced by attrition with minivans and their “15 mpg if you’re lucky” efficiency ratings. Why? Because there are precisely two kinds of car that really fit a growing family: station wagons and minivans. Those are the only ones that have the people capacity to haul two parents, two kids, luggage/miscellaneous items, and possibly the kids’ friends somewhere when necessary. If you don’t have a station wagon or minivan, either someone’s getting left behind or you’re splitting into two vehicles.

Point #2 – “Miles per gallon” is a lousy measure of efficiency anyways, because there are all sorts of fudge-factors that go into the measurement and assumptions being made. Setting aside jokes about Paul McCartney’s hybrid getting only 4 mpg or Al Gore wasting fuel flying a limo to Tokyo so he could be seen arriving in a “hybrid limo” to an award ceremony, we still have to deal with the fact that what we are really trying to figure out is how much work is being done by the engine.

Basic science, first of all: the maximum (theoretical) efficiency of a heat engine is definitively not 100%. It never can be, because it is measured by the equation Eff=(Th-Tc)/Th * 100; in other words, the hot side (Th) minus the cold side (Tc), divided by the hot side, with all temperatures in Kelvin. For purpose of reference for cars, Tc can be nothing other than the ambient air temperature, or approximately somewhere between 250 Kelvin (“Really Frickin’ Cold Canadian Winter”) and 330 (Furnace Creek, Death Valley, USA). For purposes of guesswork, a temperature of 300 Kelvin (~80 Fahrenheit, ~27 Celsius) is a reasonable approximation to work with.

Thus, the goal of an “efficient” heat engine is to generate a really freaking high Th, just shy of actually melting the engine’s parts, to do work with. For the internal combustion engine, this gets to be around 1500 Kelvin or so, with a “theoretical” efficiency of 80%… but of course that’s not really the case. First, the exhaust gases aren’t exiting the engine cylinder at precisely ambient air temperature (they’re usually more like 350 Kelvin or higher, then go through the tailpipe while cooling further before being released to the air), so our efficiency is lost by that difference. Second, there is inefficiency from “heat” lost everywhere that isn’t doing any useful work – the heat that heats up the engine parts (requiring a coolant system to avoid melting them after running the engine for lengths of time), friction between road and car, friction between car parts (mitigated, but not completely, by lubricant… again something that can’t be theoretically 100% efficient nor would you want it to be), and so on.

So we get “efficiency” in that sense… but that isn’t miles per gallon. What we are really looking for is an engine that will extract the most energy from a given quantity of fuel, given that gasoline itself has an energy density of 130 MJ/gallon (gasohol, the 90/10 whiskey mix most people are actually getting, is only 125 MJ/gallon and has other thermal properties that further reduce its efficiency for use in an internal combustion engine). In other words, we want the maximum amount of energy (in Joules or MegaJoules) to be transferred to “go power.”

Once we have the efficient engine, THEN basic newtonian physics comes into play; “miles per gallon” is based on the amount of work (in Joules, again) to (a) bring the vehicle up to speed, (b) maintain the vehicle’s speed when facing loss due to other factors (wind resistance, road friction, internal part friction, etc), and (c) safely maintain the vehicle’s internal features and control (modern engines “lose” mpg by transferring power to other things like the electrical system, Air Conditioning and Power Steering, rather than making passengers sweat and drivers use Power Steering By Armstrong).

Needless to say, the heavier the vehicle, the less “miles per gallon” it will get even if it has a “more efficient” (Joules/gallon) engine. Likewise, the less aerodynamic the vehicle, the more “efficient” it will be, which is why this 1.5-seat vehicle (that secondary “back seat” does not look comfy) can get 285 mpg without even needing a hybrid engine. And you trade “efficiency” for pickup power and other benefits, too. The aforementioned vehicle only gets this efficiency by skimming a mere couple inches from the ground (would damage its frame passing a speed bump or even a mere pothole), with a single passenger, no luggage (no luggage capacity even if you wanted to!), and with “pretty darn slow” acceleration, a “pretty darn low” top speed (less than 75 miles per hour), and only seeing that efficiency in a narrow power band best maintained by driving the vehicle around half its top speed. In other words, perhaps good for a single-shot “to work and back” vehicle, virtually unusable for almost anything else.

Yes, there’s room to make vehicles more “efficient” in the “miles per gallon” sense – but it would be nice if the environmentalist crowd would realize that there is work to be done, that reasonable cargo space (the ability for me to carry, say, 3 friends and some luggage without anyone feeling cramped) and a reasonable-height frame are not “luxuries” for all people (the roads in Colosse are lousy enough thanks), and that the “Work” (in Joules of energy) required for specific tasks can never be simply pulled from thin air.


Category: Road

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16 Responses to Terminal Inefficiency

  1. kevin says:

    So that’s why station wagons are gone. My wife and I have two girls, ages 4 and 10 months, and I could not agree more with your points about the need for cargo space (and yes, my wife drives a minivan, much to her chagrin). One other point that you don’t make but would quickly realize if you have kids. Car seats take up a lot of space. If we have a third kid, we would not be able to fit into a tradtional, 4-door sedan, which seats 3 in the back, because baby and toddler car seats take up too much space to squeeze a third child between them. So would we have to give up my Volkswagon Jetta and buy another minivan? We would not have to if station wagons were still available…

  2. trumwill says:

    Your first point serves to reinforce mine. The main problem I have with Bob’s logic is that the hybrid Durango is more more efficient for a Durango while the Civic is less more efficient for a Civic. My issue is that the Durango should be compared more directly to the Civic. Likewise, the Station Wagon is inefficient (MPG-wise) for a car and the SUV is fairly efficient for a light truck. But from a pure MPG standpoint, the station wagon is much more efficient than almost any SUV.

    (On a sidenote, I think that CAFE is a pretty dumb idea. There are better ways of going about what CAFE is trying to do. Unfortunately, these ways are not popular because they’re too transparent.)

    If the goal is to conserve gas, then we should look at MPG as the primary metric regardless of whether we’re looking at a motorcycle, compact, or extended-cab van.

    That some automobiles may be more efficient at extracting the most energy for the most pound moved but relatively beside the point. If the goal for the individual 9 out of 10 times is to get from Point A to Point B (sans cargo), and the goal for society is conserve gas, then a super-efficient 4,000lb car is less helpful than a less-efficient 2,000lb car even if by some other metric the 4000 is more efficient than the 2000.

    To the extent that we’re worried about gasoline efficiency-per-pound carried, that could be useful to in a commercial capacity where people have to carry certain loads, but as far as the rest of us are concerned the main area of concern is MPG. The goal being to reward drivers that are willing to accept the inconvenience of not having a light truck or big car handy and to encourage people to get as small a car as they can that’s big enough for what they need the vast majority of the time. That’s rarely a Durango.

    A lot of this debate hinges on how concerned we should be about consumption. I assume for my comments both at Bobvis and here that we should be. I assume that’s what the government wants. As such, the metric that matters most is MPG.

    If you’re not overly concerned about cutting back on consumption, then by all means leave it to the consumer. The questions of the environment, “energy independence”, and so on are somewhat out of the scope of my comments and are more politically-charged than I would like to get into.

  3. Peter says:

    If I were in the market for a new car right now I’d probably look at a large SUV like a Durango. Commuting from a nearby train station, I drive very little (~600 miles per month), so fuel prices aren’t particularly important to me, and it’s probably possible to get some really good deals on a large SUV.

  4. Webmaster says:

    The goal being to reward drivers that are willing to accept the inconvenience of not having a light truck or big car handy and to encourage people to get as small a car as they can that’s big enough for what they need the vast majority of the time.

    The problem with this statement is that it is really counter to what we need. We don’t need cars that are tiny, Jetson-like affairs where one person barely fits inside with only a briefcase for luggage. I drive a pretty small “sports” type car right now, and I run into problems because of the following concerns:

    #1 – short roof.
    #2 – Back window slopes down so soon that a lot of taller friends literally can’t sit in the back seats without hitting their head on it.
    #3 – No leg room in the back, as in “less than an airplane” even behind my drivers’ side seat (and as you know I’m not that tall).
    #4 – Middle console that means anyone sitting in the “middle” of the back (which makes them look like sardines in a tin anyways) has to share the No Leg Room of the left and right side people.
    #5 – No Cargo Space. The trunk is small, seriously.

    Now, is it fuel efficient? Yes, it is – in part because it’s got a standard (manual) instead of automatic transmission. In fact, overall we could do a heck of a lot better for both “miles per gallon” efficiency AND for raw energy efficiency by making the standard transmission truly standard again, since a slushbox is always slipping by at least 10%.

    If you’re not overly concerned about cutting back on consumption, then by all means leave it to the consumer.

    I’m concerned about cutting back on consumption until the point where the “remedies” pass into the point of absurdity. Asking that medium-size (mom, dad, 2 kids) families purchase a Honda Civic as their primary vehicle qualifies as absurdity. Honestly, today’s technology could easily have a station wagon getting as good gas mileage as my “sports” car (the foreign models do pretty darn well) and it would be a major step up from the minivan market. Even if one day every two weeks (about the level of what happens) I have two other people in my car, a two-seat car is insufficient for my life and my current car is what I would consider cramped, so when I am next in the market (and not under the gun) I will really, really, really be trying to get something a bit larger and with more cargo space.

    I just wish I could get an American station wagon.

  5. Webmaster says:

    Addendum: a secondary part of my complaint with the whole “hybrid car” theory is that, as proven in real-world testing, they really don’t get that much of an increase in miles per gallon.

    The reason is simple: as in the analysis above, the primary place you lose energy isn’t in the engine at all, it’s the rest of the car (accelerating to speed, maintaining speed, and other “features” like power steering or the slushbox) that’s losing energy.

    Stick a manual transmission (or the new Continuously Variable Transmission systems) in a car, improve its aerodynamic profile, and you get far more of a boost in mileage than you get simply by sticking a hybrid engine in an existing shell.

    If the “environmentalists” were really interested in “saving the environment”, this point wouldn’t have escaped them – but for them, it’s not about making cars more efficient overall but about getting rid of the “devil”, or Internal Combustion Engine, entirely.

  6. trumwill says:

    The problem with this statement is that it is really counter to what we need. We don’t need cars that are tiny, Jetson-like affairs where one person barely fits inside with only a briefcase for luggage.

    Well, no one needs a car that they can barely fit into, but a small car that fits one or two with limited luggage space is all that some people need. If such cars were available and I were in the market, I might get something like that so my wife and I would have one full and one half car between us. I’d get a motorcycle if I weren’t worried about my safety (I’m not biker material). It’d be good, if we’re trying to reduce consumption, for people that need that to just get that. People who need more can get more.

    As it happens, I barely fit in my car. I should write a post on that if I haven’t already. There aren’t many people more crammed in their cars than I am. I miss my four-door.

    But when I next need to buy a car, there are a lot of things that are going to factor in. Mileage, footprint, comfort, accessories, price, and so on. Nudging the price to induce me to buy a smaller car wouldn’t be an altogether bad thing.

    One thing that I think would happen if we based it on MPG rather than MPG-for-its-type is that we might see more creativity. More in-between cars like station wagons and large-cab passenger cars with more trunk space. Honestly, there’s a lot of variety right now. I’ve seen passenger cars with a lot of space.

    Asking that medium-size (mom, dad, 2 kids) families purchase a Honda Civic as their primary vehicle qualifies as absurdity.

    As their primary vehicle, that’s a stretch. One potential solution to that dilemma would be to get a van and counter that with a small car for their other vehicle. That’s what my parents did. I’m not in favor of closing down the market for larger vehicles. Just encouraging people that can get smaller vehicles to do so and maybe a little more sacrifice on the part of people getting larger ones. Or maybe encouraging them to get the next size down from a van. Like a station wagon. Which, if it can be designed to get the same mileage as your car, wouldn’t be so much of a problem.

    Addendum: a secondary part of my complaint with the whole “hybrid car” theory is that, as proven in real-world testing, they really don’t get that much of an increase in miles per gallon.

    Do you have a source on that? I can’t seem to find much more than allusions to studies both pro and con and all of the allusions seem to dovetail nicely with what the author wants to believe. My understanding is that it depends significantly on what kind of driving you do.

    My brother Mitch has a hybrid. I’ll shoot him an email and ask him how it’s worked out for him. He’s neither trendy nor green, so I’ll probably get the dirt.

    In any case, I’m not an adherent of the “Hybrid Theory”, which should have been evident by the fact that I was complaining that a hybrid Durango shouldn’t get a break that somebody driving “a hybrid or a plain Civic”.

    Stick a manual transmission (or the new Continuously Variable Transmission systems) in a car, improve its aerodynamic profile, and you get far more of a boost in mileage than you get simply by sticking a hybrid engine in an existing shell.

    Keep the eye on the MPG ball and these innovations are rewarded. I don’t care whither the MPG boost comes from hybrid technology, smaller vehicles, lighter vehicles, better transmissions, or some other source.

    If the “environmentalists” were really interested in “saving the environment”, this point wouldn’t have escaped them – but for them, it’s not about making cars more efficient overall but about getting rid of the “devil”, or Internal Combustion Engine, entirely.

    Let’s try to avoid taking such a broadly dismissive attitude towards people that we disagree with.

  7. trumwill says:

    Kevin,
    It really is a shame about the station wagon. We had one while I was growing up and I wondered what happened to them until I read a Greg Easterbrook column that made points similar to Web’s. Good point about the car seats. With three kids you definitely need more than a passenger car.

    Peter,
    What kind of car do you have now?

  8. Webmaster says:

    Let’s try to avoid taking such a broadly dismissive attitude towards people that we disagree with.

    This is a general (though admittedly not 100%) observation I’ve made over years – people who call themselves “environmentalists” are, 99% of the time, the “all or nothing” sort whose goal is not sensible use of resources (which I have nothing against, hence my lamentation of the death of the station wagon and of the silliness of sticking hybrid engines in non-aerodynamic cars rather than improving the car body itself, which would help whether you have a hybrid engine or not) but rather the destruction of certain technologies that they consider “evil.”

    A good example would be BHO, who sets as a goal of his policies making energy prices skyrocket and who thinks that this is somehow a good thing. This is not a sane policy, but the “environmentalists” are all for it.

    A lot of it has to do, as well, with the fact that they are repeating talking points and have no understanding of what they are actually saying. This is a sad fact, but it is true.

    If your goal is improved and sensible use of resources and you call yourself an “environmentalist”, you’re probably on the same page I am. Unfortunately, the “environmentalist” name has been co-opted by a bunch of lunatics who do things like this instead and who think that people should be forced to act the way they want them to act, and damn the consequences.

  9. Peter says:

    Peter,
    What kind of car do you have now?

    I have a 2006 Subaru Forester, which I like a lot. It has enough space to fit four people and a decent amount of luggage, without being large and bulky. In the latter respect it’s much better than the new generation Forester which came out in 2008, which is much more bloated.

  10. trumwill says:

    Web,

    Let me try again:

    Even if you feel they deserve it, please do not characterize your opponents as being uniformly (or near-uniformly) disingenuous or idiotic. There are people who can piece together equivalent dismissals of virtually any political party, group, or movement, but I don’t want any part of that on Hit Coffee.

  11. David Alexander says:

    Those are the only ones that have the people capacity to haul two parents, two kids, luggage/miscellaneous items, and possibly the kids’ friends somewhere when necessary

    I was born in the early 80s, but IIRC, only the largest station wagons based on large cars with questionable fuel economy could actually bother carrying passengers in the rear, and that was based on rear entry which was rather clunky. Once minivans finally developed doors on both sides, I’d argue that large station wagons became rather pointless because of the flexibility and comfort in seating that modern minivans offer.

    Now if one is looking for a fuel efficient minivan, the best option may come from aiming for car-based small SUVs that are common in Europe and Japan. The only car on the US market that meets this option is the Mazda5 which seats 6 people, has sliding doors, and decent cargo space.

    BTW, David current drives a ’99 Saturn SL2, and periodically borrows a ’01 Toyota Celica. He eschews driving his dad’s Lincoln Town Car due to it’s awful boat-like handing.

  12. CGHill says:

    There exists a reasonable alternative to the Mazda5: Kia’s Rondo, which doesn’t have sliding doors but otherwise fits the general description.

  13. trumwill says:

    The Crashmobile station wagon that we had when I was growing up was really quite roomy. Of course, back then we didn’t need the child seats and got to put the back seat down and kick back and relax in our owl little rec area.

    You know, David, the foreign cars had actually occurred to me though I never actually mentioned them. Since gas is more expensive over there, they have to find ways to economize in ways that we don’t (so much). Maybe that they don’t have CAFE means that they have a little more flexibility.

  14. trumwill says:

    My brother’s answer to my query:

    Average = 42 MPG (<= this is a statistically proven spreadsheet fact of all miles driven divided by all gallons purchased)

    More specific:
    Freeway 55-65 MPH = 45 MPG
    Freeway 65-70 MPH = 38 MPG
    Freeway 70-75 MPG = 33 MPG
    Local roads on cruise control 25 – 55 MPH = 60 – 50 MPG
    Local roads with lots of stop signs and stop lights 25 – 55 MPH = 35 MPG

    If you want to run the A/C, chop 5 MPG off the above.

    With a tailwind from Tenn. this past weekend, we got 48 MPG even having to sit in some traffic. Into a headwind I’ve seen low 30’s returns on 65 MPH.

    All of the above is with calculated driving, maximizing coast time, anticipating stop lights, and NOT driving aggressively (to the point that Brynne gets mad because I leave a wide gap in front of my car
    to coast when they brake, but frequently people jump in that space and I coast to recreate the space).

  15. David Alexander says:

    Since gas is more expensive over there, they have to find ways to economize in ways that we don’t (so much). Maybe that they don’t have CAFE means that they have a little more flexibility.

    The Europeans don’t have CAFE, and the Europeans tend design their engines toward higher fuel economy over cleaner air. Mind you, the advantage is that they have smaller engines on average along with slightly less car ownership and use. Plus, some countries still place heavy taxes on engines larger than two-liters. So $9 gas with higher taxes on big engines means that you’ll see some mid-size and large cars with small engines with turbos to compensate or more options geared towards smaller cars. That’s why you’ll see so-called compact people movers like the Mazda5 or Kio Rondo, and why our Corolla and Focus are called “small family cars”.

  16. Webmaster says:

    David,

    you skip the following other things in Europe:

    #1 – they have cities with seriously usable (for day-to-day commute at least) public transportation. During the whole month when I visited a family in Germany (Frankfurt area), we used their car a total of one time.

    #2 – They are packed a lot closer together in general.

    It’s a lot easier to say “use public transportation”, “use a bike”, etc when you’re only traveling a couple miles as opposed to finding that the only affordable housing for you is 15+ miles from your job.

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