Engine Performance problem
1992 BMW 325 6 cyl Two Wheel Drive Automatic 60,000 miles
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I put on quart of 20-50 Pensz oil in my 92 325i yesterday at a gas station because this regular oil is all they sold and the car was needing oil. I remembered that the car requires synthetic oil afterwards.
Is this 1 quart of regular oil I put in capable of harming the engine?

1992 model year BMW cars are not synthetic oil users, they were designed to run "regular" 20w/50 oil. Adding "regular" oil should not present any issues. "Regular" in this context means non-synthetic.