Welcome to the forum!
There are a few threads on fuel economy and one in particular that covers the D40.
Do you have any figures to give us an idea of how bad it is? Vehicle weight, driving style, traffic, towing - they all make differences but until we've got a vague idea of what you're doing with yours, we don't know how it compares to "the average".
You SHOULD be able to get mid 10s unladen on a highway run, but that is easily compromised by going over 100km/h - these brick-shaped utes have a considerable amount of wind resistance. City you should expect 12-14s and towing anywhere from 15s to 25LPHK depending on what you're towing and where you're going.