What makes cars fuel efficient?

[monroe74]

"WEIGHT is a bigger problem than HP"

I agree that weight is very important.

"Although HP has skyrocketed, it has really not outpaced weight by very much over the years."

I don't think that's true. I think our standards have shifted.

"170HP sounds like alot for a small car.... But a 3000 pound car needs this kind of HP just to be able to accelerate somewhat decently."

Here's an example of what I'm talking about. The Chevy Impala was (and still is) one of the best-selling cars in the US. Let's pick the 1980 model, just for the heck of it. That car weighed 3,344-3,924 lbs. The base engine had 115 hp. The optional engines had 120-155 hp.

Assuming the lightest Impala (3344 lbs) and the biggest engine (155 hp), that's 21.6 lbs/hp (and of course that's an overly generous assumption). 3000 lbs with 170 hp is 17.6 lbs/hp. That's what you're claiming is needed. But in 1980 lots of American buyers were willing to accept 21.6 lbs/hp, or something even worse than that.

A 2008 Impala weighs 3555 lbs, and has 211 hp. That's 16.8 lbs/hp. So the car weighs about the same as it did in 1980, but the stock engine is now 36% bigger (in hp) than the biggest optional engine that was offered in 1980.

Here's another interesting comparison. A stock 1980 Corvette had a 0-60 time of 7.1-7.7 seconds. The 2006 Impala has a 0-60 time of 5.7-8.4 sec. So the family sedan now has performance comparable to the 1980 Corvette.

"I think that performance/acceleration is not really the issue."

I've explained why I don't really agree. We have a problem because cars have gotten heavier, but we also have a problem because we've become greedy for hp. And cars with big motors still have relatively bad FE, even if you try to drive them efficiently and slowly.

The car companies don't have much incentive to sell small, light cars with small motors, because those cars also have smaller profits. And selling a hybrid is a lot more profitable than selling a car like a VX.

"even a VX looks sleek and aerodynamic compared to the overly tall small cars you see today"

The VX looks sleek and aerodynamic because it actually is. Its coefficient of drag is 0.32. That's pretty low.

"small cars tend to be MUCH less sleek these days than larger offerings"

I don't see any evidence of this. The new Civic and Prius (for example) are exceptionally sleek.

references:

http://auto.howstuffworks.com/1980-corvette.htm
http://auto.howstuffworks.com/chevrolet-impala23.htm
http://www.motortrend.com/roadtests/...ecs_price.html
http://www.edmunds.com/new/2008/chev...162/specs.html
http://en.wikipedia.org/wiki/Automob...g_coefficients