Why are cars still so inefficient ?

Question

My last car was a 1993 Ford Probe GT. It had a four cylinder turbo charged engine. If I drove it carefully it got 38 mpg fuel consumption. A friend of mine had a huge flat panelled delivery truck and he got 45 mpg. Neither were hybrids (it was 10 years ago).

I would think that all cars could get that economy and hybrids should be getting at least 100 mpg.

Presumably the need go from 0-100 in 5.0 seconds is a factor in this but if that was all it was wouldn't hybrids get better economy ?

So why don't modern cars get better fuel economy ?

Hey, chikara_neko, thanks for answering my quesion. Unless the gas fairy was secretly refuelling my car at night then it was definitely getting 38 mpg. Can't be 100% sure about the flat panelled truck but there was no reason for my buddy to lie about it.

Answer 1

Actually, engines today are more fuel efficient.

But the reason car aren’t getting better mileage over all comes down to 4 factors; consumer demand for more horsepower, consumer demand for more luxury, increased safety and increased emissions.

Horse Power,
Al long as fuel stays affordable (which is a relative concept as even with $6 a gallon gas in England there are a lot of gas hogs on the road, they just exclusively driven by rich people) people will want to go faster. Today’s entry level cars have anywhere from 106 to 150 horse power. Let’s compare the entry level Dodge Omni of 20 years ago to the new entry level Dodge Caliber of today. The base Omni had a 1.6 liter engine making 75hp, the base Caliber has a 1.8 liter making 148hp.

That’s an engine of nearly identical displacement producing almost twice the horse power. Do you have any idea how much more efficient a design much be in order to increase power by that much? After all, it’s the same gas.

Unfortunately all of the increase in efficiency goes into performance, which is made more difficult than cars from the past by the BIG reason car don’t get better mileage….

Weight.
Consumer demand for increased luxury and safety has been driving the weight of cars ever higher and higher. 8 speakers, 10 airbags, leather seats, crumple zones, seating seats, side impact protection, power windows, locks, seats, sunroofs, passenger safety cages, air-conditioning etc. The fenders and hoods of modern cars might not be mad from as heavy a gauge of steel as car from the “olden days” but underneath that skin is a ton of steel, literally, in come cases two tons.

This increase is weight means that the more efficient engines of today have to burn as much gas as earlier engines in order to move ever heavier cars at ever faster speeds.

Also, this porking up of cars over the last 20 years is not an American phenomenon ash cars in Europe and Asia have also progressively gotten larger, heavier, more luxurious and more powerful. Compare a 1986 Honda Accord with a 2006 and you’ll be looking at an econobox and a luxo-bardge and end up wondering why they have the same name.

Emissions
Emissions are parasitic to an engine, as the engine has to “push” the exhaust through the emissions system. When emission system first hit the market in the earlier 1970’s the drop in horsepower was so bad that all car companies decided to change the way hp was rated so they could then blame the sudden over night loss of 50 to 100 horsepower on the new rating method and not an actual loss in power.

Today’s emission system makes the ones of the early 70’s look like they just vent into the atmosphere. As emissions get tighter the engine has to work harder to push the exhaust through.

100 mpg car.
The fact is that with today’s technology a 100mpg car can be built, as GM was able to build an 88mpg car way back in 1992. The problem with today’s 100mpg car would be the same ones that kept GM’s Ultralite off the market.

In order to be light enough to reach the 100mpg mark the car would not be strong enough to pass safety tests unless it was made from super exotic materials. So you can think of having a choice between two 100mpg cars, one is a death trap and the other one costs $250,000. Oh, and both are bare bone stippers, with no options at all and are gutless wonders when the light turns green.


So cars today are, and aren’t more efficient depending how you look at it and there is not one thing that you can look at and say “this is the problem”. However, as gas prices go up consumers will begin to demand better mileage, and consumers always get what they want.

Answer 2

the day a flat-panel delivery truck gets 45MPG is the day i vote for bush. The reason cars cant get good MPG is that they're cars. They're heavy, huge and tend to push alot of air around. They contain large, multi-cylinder engines that fire relentlessly(hopefully) with no end in sight till the driver turns the key off. they also have mario andretti wannabes driving them. the reason hybrids dont get that kind of MPG is that they're all hype. A hybrid burns the same amount of fuel as it's parent car with the same gas engine, it just takes a little longer to do so. it's no more efficient. If people really wanted good MPG, we'd see a TON more bikes on the road. Me, personally, I dont care how bad the gas mileage my truck gets is. I'll be happy if it gets two digit MPG figures. I'd get a superbike if I wanted a fun ride that sips gas. Also, there's no way in hell a '93 probe is going to get 38MPG unless it's misfiring very badly. 30 would be more reasonable, and that delivery truck was lucky to get 14MPG, not 45. This is america, fool, we are not efficient people and we tend to say 'to hell with mother nature i want a fun ride'

Answer 3

The laws of thermodynamics limit the efficiency of a heat engine like that found in a car. You can keep beating a dead horse and squeezing more and more mpg out of an internal combustion engine but there is a limit and there is nothing anyone can do about it.

Answer 4

For one thing, cars today have alot more features, better safety structure, and safety equipment, which makes them heavier. Heavier cars use more fuel. You can still get great mileage from a non-Hybrid if you get a Honda Civic or Accord 4 Cyl, or any 4 Cyl Toyota (also Mazda or Nissan).