I had a 2007 Hemi QCab and I averaged about 15 mpg empty. I would get around 8 mpg towing. I bought a '04 CTD Qcab 2wd and it is my only running vehicle and my daily driver. 6 spd manual with no mods. I average realistically 21-22 mpg empty and have not towed with it. No issues using it as a daily driver at all. I paid $18K last year from a dealer. It had 68K on the clock. I bet with some shopping you could find a 5.9 CTD 24V pretty close to your budget with under 100K on it.