Oil level. Is your dipstick lying? Make sure you know what you've got.

[Mart]

I wanted to fill the Ol' 59 Flatty with oil for the first time, so what better opportunity to check the correlation between the dipstick marks and the actual quantity in the pan. Over the years parts can get swapped out and mismatched. Do this check so you know exactly where you are and can make allowances accordingly.
Just a quick tech short, recorded on the fly.
Take care and I'll catch you next time.
Mart.
https://youtu.be/CoissekFJrY