fuel consumption ?

[jules20112011]

Hi everyone, I am a new member to this forum, I own a pathfinder, mr3r, not sure about its age as was imported into uk 2003, guess it was built around 1998, it is a non turbo 2.7 diesel, would welcome any suggestions about increasing mpg, I have done the obvious, ie changing filters, also can you run these vehicles on sunflower, vegetable oil, I have a ford transit that I run on this and have done for several years without any problems apart from starting in winter conditions. Thanks in advance Julian.