Why has MPG stagnated for the past decade+?

Question

Cars made 10+ years ago get the same gas mileage (or better) than cars made today (excluding hybrids). Why has engine technology not evolved?

Answer 1

Engines are already about as efficient as they can be. Any heat engine has a maximum theoretical efficiency that depends on the temperature of the heat that is doing the work. Burning gasoline can only get so hot. And metal melts at higher temperatures. So there is no way to make a gasoline engine much more efficient that it is now. The only way to improve efficiency now is to make smaller cars. Smaller cars require less energy to move them.

Answer 2

There is only so much efficiency you can squeeze out of 400+ pounds of rotating mass that makes constant metal-to-metal contact.  Add to that the fact that once you do get that engine and all of it's mass moving, you're only doing that to propel a 2000+ pound car against winds reaching upwards of 100+ mph, depending on how you drive.  Add to THAT the fact that all of that power has to run through a transmission, a driveshaft (more rotating mass) a rear-end gear set, axles and wheels weighing up to 30 lbs. (MORE rotating mass), and you're looking at something that is ineffiecient from the get-go.  

I once read awhile ago that the internal combustion engine was only at 30% efficiency, and even though that was awhile ago, I can't imagine it's improved very much.

I think the next step beyond fuels and lightweight outer materials is to introduce new metals and materials in general to help lighten the load the engine has to propel.  Lighter pistons, cranks, cams, driveshafts, cooler flowing intake gasses, more complete combustion processes and cooler operating temperatures in general.  If you could focus that engine heat in JUST the area of combustion, and nowhere else, I would think that would help out, even a little bit.  

So while it is evolving, we're not at the point of making engines out of ceramic and titanium with less and less weight to spin and move about.

Answer 3

Engine tech has evolved but there are things called emmissions standards that are tighter each year.  In order to meet them there are problems with getting engines to have better fuel economy.  Look at cars made over several years (like porsche or even Nissan), they start with a motor works fine, but to meet more stringent pollution regs they wind up with losing power, so they increase the size of the motor a little to meet pollution regs and customer expectations for performance.  So you do not get much of a net gain in eceonomy as a result.

Things will change and in the last few years you have seen this with Toyota (Yaris, Corolla, not their pickups).

Answer 4

I personally believe the conspiracy theory.

The OPEC does not want more efficient cars. Neither does Exxon Mobile, Chevron, Shell, BP not to mention all the associated industries in refinaries, drilling, exploration, transportation and networking of oil products.

The auto industries have no way of overhauling the factories or the labor system without causing major chaos.

In the end, all the innovations and technologies just get buried under a hugh pile of red tape and snowball.

Answer 5

Manufacturers have to meet a government standard.  Corporate Average Fuel Economy, or CAFE.

When it was passed they claimed it would be impossible to meet without making cars very expensive.

Then they met it.  Once they did that, they stopped worrying about gas mileage.  Improvements in engine technology went to making cars more powerful.  Because that sells better.

Because of global warming there are laws being suggested to raise CAFE.

And the manufacturers say it can't be done without making cars way more expensive.

This is where I came in.  :-)

Answer 6

The problem, at least in the United States, is the fact that California emmission standards restrict vehicle design, and in turn restrict greater fuel mileage. Actually, California has many emmission standards that have no point in regards to emmissions, but they have an effect on the mileage of the vehicle.

If most of the states revised their emmission standards (not just California) to reduce them to the basic standards that they need to reduce emmissions, with the fuel system and engine designs, having a three-litre engine that gets 40 miles per gallon, wouldn't be imagineable.

Answer 7

There haven't been any huge strides forward in engine technology since we got rid of carburetors. Its not like we haven't been studying gas engines for the last 100 years. There is only so much energy in a gallon of gas and the air resistance is pretty well fixed for car travel so what part of automobiles can we look to to get more efficient? Don't forget we have all the safety standards we keep adding making the cars heavier also.

Answer 8

Engine efficiencies have advanced each year but they have been offset by increases in weight and shifts to higher performance. The auto industry claims it is what the consumers demand, but anybody with a brain knows it is what the public has been sold. Things will not change until a policy is adopted that puts a price on carbon dioxide and other GHG so that there are incentives to decrease the consumption of fossil fuels and the technologies that pollute the atmosphere.

Answer 9

Technology has evolved but it has been used to create more horsepower, not better mileage. We, the car BUYERS, are a big part of the problem; automakers wouldn't be doing this if we demanded better fuel efficiency.