Oil for a 1997 840?
I recommend using the BMW castrol 5w30 blend. It is full synthetic, or other options are redline oil and mobil one. Those are my personal choice for BMW but stick with 5w30. Hope this helps.
The above are good choices, especially since Castrol is the brand recommended by BMW. I have also used LubriMoly which can be purchased online from Bavarian Autosport (www.bavauto.com). It is full synthetic and imported from Germany.
Even a 10/40 is fine although some mechanics recommend not mixing standard and synthetics - preferring use of one OR the other. I have found that Chevron Techroline gas additive is also very helpful keeping these clean.
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