you can buy a reset tool or you may improvise and use a wire and locate pin 7 in your diagnostic connector and the other end connect it to pin 19 but you need to turn the key in the ignition first without starting the engine and you need to time it.it should only last for 4 secs from the moment you connected the 2 pins otherwise if it's about 12 secs it will reset inspection interval service light. it may sound funny but i just did it on my BMW 320i 1988 exact model as what you have.
reset oil chang light of 2006 BMW 750li
Reset inspection light on 1989 bmw 325i
try to reset oil light on 528i bmw year 2000
How do you reset the oil service warning light manually on a 2003 BMW 525i?
How do you manually reset the oil life monitor on a BMW 525i
Change the oil.
How to reset oil light on bm,w 750li
To reset the oil service light manually on a 1996 BMW 318i, disconnect the battery. Leave it unhooked for 10 to 20 minutes.
You need two special BMW reset tools.
You must have the special needed tool to reset the oil indicator light.
Burn the car....
To reset the e39 oil inspection light, a special reset tool is needed. The tool is plugged in the data port under the hood, and it will allow the computer to reset the light.