My cousin had a mid/late 90s 318ti. He routinely got ~30 with it and even better on the highway. Needless to say it lacks the power of the higher trim models. But, it gives you the beamer feel.
I'll ditto Smurf's more expensive repairs and premium fuel costs negating any cost savings benefits though. It definitely lisn't a cheap vehicle. I remember my cousin doing a brake job on that car and it cost him 2-3X what it would have cost me to replace the brakes on my Paseo.