When will people learn that "efficient" doesn't mean good gas mileage?

Question

It's like,
Al: What gas mileage does your truck get?
Jon: 15 mpg.
Al: Mine's more efficient than yours! I have a 4.0 v6 and get 18 to the gallon!
Jon: But...i have a 6.0 V8 that makes nearly twice the power of your v6 but only uses slightly more fuel...therefore it IS more efficient.

My question is, why do people think efficient means better gas mileage?

bfriedmanns, what i'm trying to say is just for that scenario i wrote. a car that gets 45 mpg that made a certain amount of power would be more efficient...but in my example the vehicle that got 15 mpg is more efficient.

Answer 1

Efficient in mechanical terms means that an engine is producing maximum power on a given amount of fuel and producing minimum pollutants. When you see an engine belching black smoke, it means that the engine is not burning all the fuel that is being put through it. Internal cumbustion engines are designed to operate at maximum "volumetric efficiency", meaning that they are nearly completely burning all the fuel introduced into them, which for one engine could mean using one gallon to move the vehicle 30 miles, or one gallon to move the vehicle 10 miles. An engine that uses one gallon to move a small vehicle 30 miles is going to suck at pulling a 45,000 pound trailer, but a Cummins diesel engine that can pull 45,000 pounds 30 miles at 65 miles an hour using five gallons of fuel is going to be worthless in a Ford Festiva. Efficiency, however, is measured on many levels. If I drive my Neon 25 miles to work by myself, which I do five days a week, it takes me less than two gallons a day for that task. If I drive my Odyssey, it takes me closer to three gallons a day to complete that same task. So, the task of getting myself to work and back is more efficient in terms of fuel usage if I drive my Neon. However, if I were to carpool, the net efficiency strictly in terms of fuel used to complete the task of getting two people to work and back is doubled. Or approximately doubled. You get my drift. So, in a nutshell, if I travel alone in my Neon the same route to work and back as my neighbor alone in his Hummer H1, assuming I had a neighbor with a Hummer H1 who lived and worked the same places as me, it would be more efficient in my car than his. But, all bets are off if he carpools with five other people on the same route.

Answer 2

I beg to differ. Having twice the power....are you using that power for a job that requires twice the power or are you just hauling your butt around? Most of the time I bet the latter.

So, vehicle 1 hauls driver at 14MPG and vehicle 2 does the same job at 45MPG. Which is more efficient? And if the fuel costs come out of your wages, you know which vehicle you are gonna choose.

Answer 3

In order to compare anything, the items must be quantified in order to have valid results. Now, you say efficiency doesn't equal good fuel mileage.....possibly. If you are comparing HP per liter of displacement, or HP per liter of fuel burned, then engines of several sizes and types can be measured in relative terms. In this case, the engine with higher HP per liter (in both respects) could be deemed "more efficient." However, when encompassing more variables, vehicle size and weight, cargo capacity, etc... the numbers can change quite a bit.

Answer 4

Good gas mileage doesn't mean good emissions either. To have good emissions you compromise good gas mileage.

If you don't believe me talk to someone with a California emissions vehicle.

Answer 5

thats is what the media taught most people.