I once had a gummed up machine it took four days to free up. It turned and sew fine, but it took repeated oiling and test running the machine a couple of times a day before it turned as light as it should. I used spray can oil and regular sewing machine oil at the time. I remember something suddenly released the fourth day, I had again added a bit of oil to all the oil points and it did the trick. Another common thing is missing a spot or two; all joints, gears, levers, hinges knobs, needle bar needs to have the oil seep in where it should, and it can take a bit of time for dried up oil to dissolve. It's often more of the same that does the trick, unless there's layers of grime and thick grease, you should get by with triflow. A good spray can oil can speed things up too.