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What fuel is proper for 1980 323i, 95 or 98 octane?

95 unless youve modified the engine with a slightly higher compression ratio and had it mapped to run on 98.

modern cars have active knock control and can effectly adjust themselves to run the best they can on either octane fuel.
old cars cant, so cant take advantage of 98 unless being mapped to run on it.
on old cars its just not worth paying the extra for 98.

Guys who knows how to properly adjust ignition angle should have book where they can find information about correct angle for particular octane fuel. So you can choose correct ignition angle either for 95 or 98 octane fuel.

I've heard people say the higher octane fuel has better quality control, so is less likley to contain contaminants. Sounds unlikley, but I drive the 323i so rarely I always use 98.

In my usermaual it say "min 98 octan". Thats what i use on my car.

Bens engine (although higer compression than most) sounded shit on low octane shell fuel, pinked like fook when he was getting it mapped, up to the point where we had to drain the tank and get shiny new high octane fuel to continue

You all have to chech your engines for correct ignition timing angle. After setting it correct you can start to find best fuel for your car.