2000 Jaguar XJ8. I took my car to get the oil change and the next day, the vehicle started to make a "knocking" noise. I checked the oil level to make sure that everything was being lubricated and the oil level was extremely low. I added approximately two quarts (the vehicle takes approx seven), but the problem still persisted. I called the business that performed the oil change and told them that I thought it to be a rod knock. However, when I took it to another mechanic, they told me that the "knocking" was coming from the valve area; not something that could be associated with a faulty oil change. What do you think then? It just seems too extraordinary to be coincidence.
The noise your probably hearing is the upper tensioners. They could have gone bad due to lack of engine oil. Such as not enough oil, you have to have the valve covers removed and have them inspected. There is a plastic piece that will fall off and it could cause a timing chain to break if it gets stuck, get it checked as soon as possible.