Metal against metal = clean out debris and apply proper sewing machine oil. Plastic = clean out debris but otherwise leave alone.
I recall being in the late, lamented Theobold's Sewing Machine shop in Luton and hearing Robert's horror stories of machines being brought in to be fixed because the dopey owner, thinking 'one oil's the same as another' had put *cooking* oil on the moving parts
The only thing triglycerides and hydrocarbons have in common is that they are both insoluble in water. Don't put the former on machinery and don't cook with the latter!!!