You can put a BMW 525 engine into a BMW 325. The motor mounts will need to be changed. The 525 engine motor mounts will not match the 325 engine compartment.
The 1990 325i has a M20B25 motor. The earlier 1990 525i had the same motor, a M20B25, whereas the later 1990 525i had a M50B25.
the BMW 525i is larger than the 325i they both utilize the same engine an inline 6 cylinder. 325 may be 200 lbs lighter.
1992 BMW 325i
What year 525i? The oil recommendations vary. Not all 525's use the same engine or the same oil.
50w-30
If you asking about the engine type, the 325i is a straight-six not a V4.
The engine control module on a 95' BMW 325i can be found on the transmission. The transmission is under the hood, near the engine.
The best oil you could use for the 525 i is magnatec or 20 w 50
On the top of engine in a casing in the front of the engine
No
Yes
No, the 1995 BMW has a M50B25 engine, which is basically totally different from the older 1989 BMW which has a M20B25 engine.