I recently changed the oil in my '01 Focus when I noticed that it was pretty low. After I was done I started my car and heard a sound that was brand new. The engine was making this low noise, almost like a diesel truck, a sort of knocking. A keep a good eye (or ear) on my engine sounds and I'm positive this wasn't occurring before the change. Once I heard this I kept it parked until I could get it to a shop. They checked it out and said they couldn't find a problem. They went ahead and change the timing belt but the noise persists. I know the oil change could be completely unrelated but it seemed odd. Any ideas as well estimates on repair would be much appreciated.
<br/> Also, the engine cap said that it required 5W-20. But I looked at a repair manual for that year and engine and it said to use 5W-30, so that's what I used. I don't know if that makes a difference.