Originally Posted by
Sant
Because a seat in business class is heavier than one in economy, is that why the fuel surcharge is higher?

Yes in exactly the same way that the average person travelling from Australia to Singapore, is heavier than the average person travelling from Australia to Dubai is the reason the surcharge to SIN is > the surcharge to DXB, despite being only half the distance.
Illustrated most effectively by EK405 which travels MEL-SIN-DXB. If you take this flight only as far as SIN the surcharge (in Y) will be $165. If you take the flight all the way to DXB the surcharge will be only $155.