I'd say expect more of 30-35 mpgs, and as for the block heater, if its in good shape, you most likely wont need it. My has started in subzero temps with 15-50 wieght oil in it. Good luck and check out the spring perches for rust, I just noticed some on my 98

__________________
2002 G500 74K
1998 E300 200K and rising
1995 S600 73k


"Some people spend an entire lifetime wondering
if they've made a difference. The Marines don't
have that problem."-Ronald Reagan

"Never tell people how to do things. Tell them
what to do and they will surprise you with their
ingenuity."-General George S. Patton