Machines

[Diaphone Jim]

I've been changing oil for about 65 years for myself, GF's, parents, kids, grandkids and friends.
I pour the drained oil into old milk or water jugs for recycling. (It is amazing how long oil recycling has been available).
I can't remember the first time I looked at what I had drained and wondered how it always happened that I had replaced it with substantially more.
Yesterday it was 3 5/8 quarts into my Pathfinder, as called for and perfect on the dipstick before and after.
Today I measured the oil I drained at 3 quarts.
This difference may be a less than I've noted 10+ times with 5+ vehicles.

Anybody noticed this phenomenon?
Anybody know why?
I have some ideas, but none I like.