In the world of used BMW models, a few champions of the flock rise above the rest in terms of popularity. Its Biggest Failing Isn't Actually That Bad1992 bmw e36 325i blue front BMWAs mentioned above, the M50B25's greatest weakness lies in its cooling system. Easy To Keep Running1991 bmw e34 525ix cutaway diagram BMWIf you're starting on a classic BMW hunt as an enthusiast, your attention would likely fall on an M model. There are several instances of the M50B25 engine lasting well over 300,000 miles. 1991 bmw e34 525ix silver side BMWAs BMW's halo M cars continue to climb in price, leaving more and more folks in the dust, we, as a collective of enthusiasts, must adapt.