What is the most fuel efficient vehicle on the market today?

Harry, I assume you mean cars. And ones that aren't 6 figures.

Currently sold is now the 2007 Toyota Prius hybrid at 46 mpg EPA average.

It used to be the Honda Insight hybrid at 70 mpg but they quit selling it because no one in America seemed to care about buying fuel efficient cars, so after 6 years of terrible sales, they quit making it.

If you don't mind driving a used car for a much cheaper price here you go.

The 2000-2006 Honda Insight

1998-2006 Volkswagen Beetle/Jetta TDI (They quit selling the diesel last year) got between 44 - 49 mpg on the highway.

1988-1991 Civic CRX HF was EPA rated at 49 city/52 hwy

Any 1988-2007 Kawasaki Ninja 250R is the most economical motorcycle and gets 75 mpg, and they are very reliable, fun and very fast. I have owned 2 of them. They are less than $3k brand NEW! And you can get a used one for a lot less!

(Going into summer, seems like a good year to learn to ride a motorcycle like you've been telling yourself for 10 years. Tell the wife it's to save money on gas prices which will probably hit $4/gallon, which technically it is. This year she can't argue with that!)

Good luck Harry on your fuel economy quest!

It really depends on where you drive:

--Hybrids use breaking to regenerate their batteries. Hence, the more stop and go traffic you are in, the more efficient they are. Of course, auto manufacturers are more than happy to charge you a significant premium for such efficiency.

--On the other hand, if you drive mostly on the highway, I'd look for a nice 4 cylinder sedan--a Honda Accord can get you 35mpg (up to 40mpg with a Toyota Corolla if you are willing to give up some comfort) while lacking the limitations of the puny engines of the Prius or Insight.

--If you can get your hands on a new turbodiesel (like the ones offered across the pond), these are, buck for buck, the most fun to drive and efficient cars around. If I remember right, an Audi A6 TDI can get between 45 and 50 mpg highway. Additionally, all the new European diesels can run on 20% biodiesel blend (biodiesel does not contain sulfur and is thus 'greener' than regular fossil fuels).

Depends how much money you have to spend....

But Electric Vehicles are the most fuel and energy efficent.....

The Telsa motor Company has made the "Tesla Roadster"

Despite the hefty $92-$98000 price tag it is

100% electric

0 to 60 mph in 4 seconds....

135 mpg equivelent....

Over 200 miles per charge

less than 2c per mile......

It won a few awards including Best Inventions 2006 - Transportation Invention

If I had the money I would buy one of these and drive around the country if not the world

They are a cool sporty looking car....

Otherwise definatly the prius cars are or even motorcycles if you are looking at something other than a car.

Depends on the task the vehicle is for.

A wind or kite surfer is probably most efficient individual transport.

Bulk carrier ships are very efficient per tonne/km.

Tracked electric vehicles on land, trains, trams, mag-lev etc, especially if you include the embodied energy of track compared to a metalled road.

Airships are pretty good once you have produced the helium.

As for cars, as mentioned the Prius is the most available; but pure electric vehicles are much more efficient than infernal combustion. There are ones available (just not easily) from powered bikes, motorbikes, drag racers, quad-bikes, neighbourood vehicles to the Tesla www.teslamotors.com or the 5 seater SUT www.phoenixmotors.com. most are sold out of this years production (GM said there was no demand when they crushed their EV1 www.whokilledtheelectriccar.com )

Electric provides max torque at 0 rpm, from cold, no complicated transmission or coolant or injectors, low maintenance, quiet, smooth, smell free, refuel at work or home from renewable energy, free parking in some cities like Westminster...

Well, I guess a motorcycle, as the others say. It's light, effective, fast, and economic. But if you want more seating capacity, get a hydrogen car (out in Australia in 2010). the only thing it emits is clean water, safe enough to drink. But, despite the answers I have given, the government has thought of scooters for a start, but the cons come quick. Although it has a seating capacity of 2, same as a normal motorcycle, it goes at a slow speed and isn't that fuel efficient. Still, I'd go for a motorcycle.

The most fuel efficient vehicle would be a motorcycle although I'm not altogether certain which motorcycle is the most fuel efficient.

Honda Insight has boasted the highest gasoline fuel efficiency in the current market. However, there are different categories of green vehicles. Hydrogen, electric, bio diesel, and natural gas are all options.

You've got to qualify this question: what purpose, what medium?

Although I'm partial to bicycles, they do use tiny amounts of hydrocarbons on chains and in their bearings. And manufacturing the aluminum, carbon, steel and other materials requires a significant energy infrastructure.

Wind powered vehicles are made of plastics, which are made from petroleum derivatives. And, as opposed to metallic bicycles, they eventually wear out due to UV-imposed deterioration of the plastics' molecular bonds.

There won't be a definitive answer for this without narrowing down the question's scope, but here is a novel candidate: hot air balloons. Current manlift-capable models are made of petrol-derived synthetic fabrics and of course all hot air balloons need some natural gas to heat their envelopes. But I bet it is very little fuel compared to many vehicles, because you extinguish the flame (except for a small pilot light I believe) except when ascending. When in level flight, you just coast downwind.

And, just a thought, why not make them from some kind of cellulytic fiber like jute or cotton, or even paper? I played with homemade tissue paper hot air balloons when I was a kid. They had a wire hoop to give the base rigidity and the rest wa made of very thin tissue gift wrap paper. We heated them over camp stoves or small wood fires. They would sail very far before the air cooled and they descended.

A motorcycle, by FAR. The reason is they are so light and normally only have 2-4 cylinders (unless you get a big harley) I have a Suzuki GSX-R600 and it costs $8.00 to fill up every 2 weeks with super plus fuel and I ride about 5 hours a week, no joke. They are starting to come out with hydrogen motorcycles, also.

Did you know that when motorcycles first came out they got over 100mpg?

my aunt just bought a civic. its gas powered but tis also powered on natural gas and electricity. Like it can go so far on electricity then natural gas kicks in to charge the battery and if thats not enoguh the gas kicks in,