With full tank of gas, I can do about 375-380km(65% City, 35% highway), and drop to about 320-330km if I really push her hard. Go for V8 W140s if you can....they give the BEST compromise between MPG and Performance, IMO...
As for steering wheel, it turns back when the car is at motion(say, 5-10mph and above)...but at extrem low speed(let go of gas and let it glide forward), the steering won't return.....and that's normal..
Andy Kuo