I don’t think you fully understand the bsfc numbers.
If you had a motor making 500hp uncorrected, and it was using 250lbs/hr....... the bsfc would be .50.
If you added 3qts of oil to it and it lost 50hp...... it would still use the same amount of fuel....... but the bsfc for 450hp and 250lbs/hr would become .555
Any power you lost from the extra oil in the pan hurts the bsfc number.
The more it lost, the more it affected the bsfc.
