How much lighter weight to save fuel?

IamtheGaitor

(Moved from Social Room)

In the ''shop front'' of the magazine there is an article about Duvalay lightweight mattresses. It states ''If memory fibre is also used in the soft furnishings, an overall saving of 11 1/2kg would be made, making a significant impact on fuel costs''

So, just wondered how much people consider lightening their load by replacing standard items with lightweight ones  in order to save fuel? In this example the matress alone costs £499.95 so if you bought this and also had your upholstery done I reckon you would have to live to be about 1000 and be on the road 24/7 every day of the year to recoup this sort of amount but am I wrong?