Definition: Gas-guzzler

http://en.wikipedia.org/wiki/Gas-guzzler

Gas-guzzler
Vehicles by the GM marque Hummer are among the most prominent and most 
commonly satirized gas guzzlers.

Gas-guzzler commonly refers to a vehicle that makes inefficient use of
fuel.

The term came into wide use to describe the "Gas Guzzler Tax" and after 
that while discussing environmental concerns related to climate change 
and smog.

Nowadays, gas-guzzlers are often SUVs or other semi-large vehicles that 
qualify as light trucks, so they do not need to obey the minimum fuel 
economy regulations of cars; however, gas-guzzler can also refer to 
classic cars (mostly American ones with large displacement V8 engines) 
and other cars that have poor fuel economy. For example, a Lamborghini 
Murcielago, a Plymouth Roadrunner, and a Chevrolet Tahoe might all be 
classified as gas-guzzlers, though they are very different cars.

Common examples of 'gas-guzzlers' include:

     * SUVs
     * Pickup trucks
     * Full-size vans
     * High performance supercars
     * Some luxury cars.
     * Most old cars can be regarded to have bad fuel economy when 
compared to similar modern vehicles.


Reasons for bad fuel economy

There are generally three large reasons for bad fuel economy in all of 
the cars mentioned:

     * Large displacement engines. A large displacement engine requires 
more fuel to run it than a smaller engine, with the only exception 
applying to forced induction engines.
     * Small displacement engines. An excessively small engine often 
requires more fuel to run than a moderately bigger engine which can 
deliver more power per piston bore than its smaller equivalent. A 
smaller engine has to work twice as hard to deliver adequate power, thus 
consuming more fuel than had the engine had a slightly bigger engine 
capacity. This situation is often found in Ireland[1] where a backward 
motor taxation system is used which taxes cars based on engine CC's.
     * Heavy weight. A heavy vehicle requires more work to accelerate 
than a lighter vehicle, requiring more powerful (larger displacement) 
engine with higher fuel consumption to achieve a similar power-to-weight 
ratio.
     * Large drag coefficient. A less aerodynamic vehicle must deflect a 
greater volume of air when moving at the same speed than a more 
aerodynamic one. To overcome this drag, a more powerful engine with 
higher fuel consumption is needed.