Oil! Oil! Oil!
It really does not matter how new or old a sewing machine is when it works properly. The key to keeping any sewing machine operating at its best is to keep it properly lubricated.
Where? Place one drop of oil wherever metal touches metal, wherever parts turn against each other, and on the hook race. Always use pure, clean, stainless, and refined sewing machine oil. Never use 3 in 1 lubricant. Never use WD40. Never use auto motor oil. When lubricants get old, remove them with solvents like contact cleaner. Blow and brush away encrusted - decayed lubricants. Add fresh oil.