Dont be impressed too quickly.  30 litres for 240 km = 19 mpg (US Gallons).
It looks like you did your calculations for Imperial Gallons which are ~20%
bigger.
Any way its about right.  Its hard to do much better.

A canadian friend would always brag that his car got a lot more miles to the
gallon in Canada ;-)

cheers,
Steve Cotsford