in all honesty pretty much nothing. depends on your driving style really, if you cruise at speed then the 2.5 is going to be better, and if you sit in traffic all day in idleing then its going to make no difference. 2.5 is better as a restoration project as youll be more happy with the extra power on tap (over half as much again as the 1.8What is the difference in fuel mileage ???? with the 1.8 vs the 2.5 ? given they are both in tip top shape. thanks
redline for the eta is 4500rpm where the 2.5 is 5500Love my 87 325E. True, not as quick off the line as the smaller 325i 2.5--the 325E actually is a 2.7L. But, with the 5spd tranny it is very torquey, and reaches max torque at lower revs--the tach redlines at 5-6 rather than the 6-7 rpm of the 325i. Lower revs and fewer moving parts = longer lasting. I have 186k and no re-build yet. No oil being burned. Great gas mileage, too. 26 city 32 highway.