OKEY DOKEY, here's the scientific explanation for the sudden drop in oil level. If you look at the M103 sump you will see that is has a slope in rearmost part of the pan. With the sump full, the level on the dipstick reads normal. As oil is consumed and the level drops, the apparent change in volume indicates less when the sump is full. Volume vs. capacity. As the level gets lower, the sump internal volume decreases based on the decreasing size of the available space, so..the same amout of loss looks greater as the space that is losing oil is now smaller than when the sump is full. If you've ever poured something thru a funnel that has straight sides leading into the tapered protion you will notice that with the same size opening in the end, when the fluid level is still high, it seems to drop much slower than when the fluid level reaches the tapered portion. Then it apparently drops much quicker. I saw this on Mr. Wizard last week.
Thought I'd pass it along so all of you could explain it to your grandchildren whilst sitting next to the crackling fire..
1987 BMW 325