(I’m smoking 'em on full tank of gas)
This line refers to a technique used by models to reduce their appetite. Which is known as Chain Smoking , and modelling for such a large and expansive company such as Versace, is very stress inducing. So the model (in this case Gaga) , would most likely smoke an abundant of cigarettes to maintain her appetite during the photo-shoot. Since gasoline is used in lighters, and is being used repetitively, she is saying that a whole tank of gas is needed to light all of her cigarettes.
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