According to this article the US vehicle fleet averages roughly the same MPG this year as it did in 1980, fully 21 years ago. Now, I understand that this stat doesn’t present a completely accurate picture since there are a greater percentage of gas-guzzling trucks and SUVs on the road these days, but still…
With all of the other advances in vehicle engine technology in the last 20 years [many 4 cylinder engines on the road today, for example, produce more horsepower than the huge, heavy 318 V8 in my 1985 Diplomat], why hasn’t there been more of an increase in gas mileage? Surely this would be a selling point with consumers - even if gas isn’t prohibitively expensive, it is a very obvious expense which your average consumer would like to see reduced…
So, what’s the deal? Is it all a big Chevy/Mobil conspiracy like my hippie roommate claims? Or is there some overriding mechanical reason that prevents these engines from being much more efficient than they are now?
Well flawdlogic I’d say your logic is flawed (sorry…couldn’t resist).
You are assuming that consumers are rational…they aren’t.
I’d say you have two things at work here. First and foremost is that Americans like powerful, speedy cars. They are quite happy to trade a few miles-per-gallon for a quick start off the line rather than put-putting up to 60 in 30 seconds. Good acceleration and good MPG are almost completely at odds with each other.
Secondly, and I’m not an engineer so I can’t say for sure, I don’t think there is a whole lot more to be squeezed out of the good old internal combustion engine. There isn’t a never-ending rise in efficiency to be had. Rather, it’s more like a falttening curve where each incremental improvement in fuel efficiency is harder to gain than the last improvement. At some point there just isn’t a whole lot more to be gotten out of such an engine and you have to start decreasing acceleration times and maximum power to get fuel efficiency (in which case you are back to point #1).
Consumers are rational: the answer is that MPG is just one small part of the overall decision of which car to buy. After all, gas had been cheap from 1986 until just last year. (Another part of the problem is that most people use their cars mainly for urban commutes, where you’re going to get crappy milage regardless.)
If gas prices were to go up and stay up for several years, as they did in the '70s, then you’d see consumers and car companies obsessing over milage again.
I’ll leave the question of whether there are large gains in milage available to the engineers. It might be useful to compare US cars to models sold in Europe–gas is much more expensive there.
There are a number of mid-size cars (the Ford Taurus immediately comes to mind) for which both 4-cylinder and 6-cylinder engines were offered. The automakers will tell you that demand for the 6-cylinder models completely overwhelmed the 4-cylinder option, except maybe in fleet sales.
Detroit would be just as happy to have customers push for their smaller engine sizes – it would push up their CAFE (Corporate Average Fuel Economy) numbers quickly and painlessly. However, as has been noted, gas mileage is only one factor.
Air-con is a huge culprit, this was not anything like as common then as it is now.
Next take a look at how cars in a particular class have grown in size.
For instance the Mini was a light small car but if you were to look at its equivalent today you will find it has grown in size and weight.
You could do the same for almost any car, add to that the use of catalytic converters which sap power, all those sound systems, more powerful headlights, wider more grippy tyres, airbags, sound damping, larger seats.
I wouldn’t be surprised if the traffic is heavier too resulting in a poorer urban cycle.
If you were to put a modern engine in a stripped down car without a cat I’ll bet you would get some impressive figures.
cost vs. risk & demand
e.g.,
R&D reduces short-term profits. CEOs are often struggling to fix their current stock price.
One way to improve mileage is to make the car lighter (lighter materials) but this make the car less safe in a collision, etc.
People will still buy low-mileage vehicles. Mileage is but one of the factors in a customer’s criteria.
But check out some of the new hybrid vehicles that are starting to be sold in the common market. Those have a significant increase in MPG. They’re still too expensive for most people though.
Go back and compare a 1982 Honda Civic with a 1998 one. The differences in gross weight and vehicle size are just amazing. Japanese cars, once derided for their small size and fuel efficiency, have become every bit as hulking and overfeatured as the American cars they replaced.
Sad.
-Ben
Both of you neglect the difference between size and weight. You could say that the “density” of cars it a LOT less these days. Per size, they weight a LOT less. This has to do with a lot of factors, such as:
o The virtual elimination of a frame (some luxuries and trucks aside)
o Thinner metal - MASSIVE savings.
o Substitutes for metal - aluminum, composites, plastics, even magnesium are super-light. I saw a deck lid (trunk) at an integration shop, full size, light enough to lift with single hand, no real effort.
o Motors themselves weight less, due to lots of re-engineering and materials changes.
It’s easy to see that a car can get bigger without necessarily adding weight. Since Ford made popular aerodynamics (Taurus anyone?), increased size doesn’t necessarily mean increased drag, either.
To clarify, what I meant by that was a stamped piece, not on the car, with no pistons or springs to help you. 
Which just illustrates that American consumers are demanding larger cars. In Japan and Europe, there are still plenty of cars which are as small as the '82 Civic. There’s also the fact that gas is so cheap in the US. (Gas is cheaper than in the late 70s, isn’t it?)
Every buyer has his own reasons for buying a thirsty car. For example, I’m 6’4" tall, and many tiny cars are a perilously snug fit on me. In addition, when I ask a salesman if I can tow a 1700 pound trailer (my small fishing boat) with his micro ride, he gives me a sheepish look and shakes his head. No. I drive a GMC pickup that I really don’t need except for the trailering. Mrs. Nott’s '98 Pontiac Bonneville is much smaller than my long-ago '59 Bonneville, and it gets better gas mileage than the old barge did.
Another aspect to the gross weight issue is safety. Now I have no doubt that the modern “mini’s” are, pound for pound, stronger and more impact resistant than cars their size where 20 years ago. But if you or a one of your loved ones were ever in a serious collision, ether vehicle to vehicle or vehicle to object, lets hope there’s as much steel between them and the source of impact as possible.
I recall a few years ago a growing sense of outrage that when a monster SUV collided with a Geo Metro like vehicle, the metro became a hood ornament. What surprised me was the complaint wasn’t that the Metro was a death trap, but rather that the SUV “made” the Metro a death trap.
A side point to the weight issue, the first car I ever owned was an early eighties Dodge Colt (made by Mitsubishi). It was a small, two door, rear wheel drive car. Where I live we get a good amount of snow and that Colt, even with rear wheel drive handled snow better than my girl friend’s 96 Ford Escort, which has two more doors and front wheel drive. Simple reason, it was heavier.
Not that light vehicles are inherently bad, but you are trading safety for MPG.
Look at it this way, Ennui: If everyone rode bicycles, there would be a negligible number of vehicle fatalities. If almost everyone rode bicycles, and 10% of the population started driving Geo Metros, you’d get people complaining that Geo Metros make bikes into death traps.
One of the (perhaps justified) complaints people have against SUVs is that they are not engineered to be “compatible” with cars on the road; for instance, their fenders are much higher off the ground, so in a collision they don’t hit the car’s fender, but the engine block (or with a little upward momentum in a side collision, barrel through the driver’s window and into the driver’s cranium). Given that the vast majority of SUV’s are doing the same commutes that cars are, it might make sense to design them to be a little more “car-friendly”.
Now if you’re paranoid about your safety, buy an M2 tank, but be prepared to pay lots on gas, and your ride comfort will also be pretty crappy.
I’m not saying that everyone should ride bicycles here. I do, fully cognisant of the risks. My fuel economy is way better than yours too 
If what people are really looking for is rapid acceleration, wouldn’t some sort of flywheel technique be the answer? You slow down or stop-- the flywheel spins faster. You want to accelerate-- the flywheel transfers its momentum to your drive train.
Because we live where fuel is relatively cheap, economy isn’t a really big issue for a lot of people. We like power… alot. We equate safety with the size of the vehicle and this is certainly not always true.
Travel to countries where fuel is grossly expensive and you will see many more smaller cars that will get the most mileage out of that expensive commodity. In some European countries your insurance is based on engine displacement, smaller cars cost less to insure than larger vehicles or sports cars. You will see more turbocharged and diesel powered vehicles as they get better gas mileage or are cheaper to operate.
Why don’t have an automaker here that would offer a minivan that was powered by an efficient turbo diesel? Because I would be one of the only people that would want one.