Gas Guzzlers, per se, only exist in the minds of journalists and politicians - i.e. people that don`t live in the real world and actually believe the things they say or write.
I suspect the phrase originally came from America (the clue is the word "gas") where single figure mpg was not unusual in years gone by.
My other concern is the adoration of hybrids, such as the Prius. I`m sorry but they are driven totally and completely on petrol like a lot of other cars. Any electricity generated, stored and used to drive the car is derived from burning petrol. It is not magic - and a lot of more conventional cars (mostly diesels) are actually more economical in real world use. And don`t get me started on what it costs to manufacture the extra batteries, motors etc. and when it comes to disposing of them at the end of their (limited) life................