Keep the bobbin area clean and put a drop of oil in the bobbin race once in a while. Many machines have embedded silicone in the gears so self lubricating. Metal gears are not self lubricating. The housing on newer machines cannot be taken off without damage unless you know the correct way. I sit and watched a tech work on different machines (long story) and he oiled every one once inside from new models to older ones. One he drenched in oil and put in pan to drain, others he added drops.