create an object such as a sphere, then in lomUtils set the type to lod, add as much lods as you want and set the distance values. Now create some fuel tank LODs, set the LOD id's of your tank parts to id's you specified on your lods object, and link all your tank LODs to the lod object. and center the lod object on your tank.
I hope i got this clear enough.
BTW you may want to make your tank material "per pixel specular", looks much better than standard.
Good luck.:thumbup: