fuel is very bad becuase I floor it all the time... but driving from qld to vic.. i was getting 500km per 60l but that was doing 130km the whole time... at 3300 rpm, where 100km/h is only 2000rpm.
rust not a problem at all.
when your buying if its a 3ltr u wont have a problem, but a 2.4 make sure its had head work. Also heaps of them are accident damage. Umm.. also, diesels last forever but cost heaps to maintain, so make you get a well maintained one or you will be in for big bucks.
Since having mine the main expense was the head.. then after that i had most belts and hoses replaced just due to age. Also a CV joint boot needed replacing but they break when something from the road flies up and hits them. Other than that I got a well maintained 2.4 with full recaro interior and it has been great and only costs $550 a year to insure (and im only 19).