Granted Patent
Utility
US 4,869,346 · App. 07/085,170
Automatic crankcase oil change and makeup system
Inventor:
Donald M. Nelson
Patented Case
View Patent ↗
Granted: Sep 26, 1989
Filed: Aug 14, 1987
Inventor
Donald M. Nelson
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.