The manual for my Star says that the universal joints should be oiled with 600W oil. However, they all have an Alemite grease fitting instead of an oil plug. Should I grease these or disassemble and clean them and then fill them with oil?

Do You own a car built by Durant? 1925 Star Touring

Vince,
The grease fittings were added later on by the owner. Apparently, you have the double Spicer universal joints which are designed to use 600W oil. This assembly can be problematic due to leakage if not serviced regularly. If it rattles perhaps you need to remove and inspect the joints and seals for wear. Close inspection will reveal the construction details. Grease was probably used to try to prolong the life of a worn out universal but it doesn't lubricate as well with this type of joint.

Don

Do You own a car built by Durant? 1923 Star touring, 1927 Star Coupe

Vince:
You can buy new oil fittings from McMaster Carr.

Do You own a car built by Durant? 1924 Star Coupe