the pre 94 bmw 520i was fitted with a m20 engine which has 129bhp not sure of the top speed fuel consumption will be bad if you drive the car hard always or should be around 7 to 8 km per liter if the air flow sensor is ok.timing belt needs to be changed every 30,000miles.quite a nice car for that money check where it has been maintained though
the post 94 bmw 520i was fitted with a m50 engine which has 150bhp timing chain, most ones came with the face lift with bigger kidneys in the front grill
better get a brand new import always if available.