You said you got your oil changed in March, this is the end of April. Have you though to check the fluid levels in all that time? Have you seen oil left in your parking spot? I'm betting no to both questions. And the simple fact that many people don't seem to know is that if the engine RPM goes low, less then idle speed the oil light will come on and if the reason it goes below is that it has started to have other problems and they cause the engine to stall you will see the oil light come on. So everyone went with the oil change (sue the bum) nobody wanted to question you on just what kind of knock you have. They think it is a rod knock and some nut case wants to put trans fluid in it like it would cure a rod knock. Do you know idler pulleys and tensioners can have a knocking noise? You need to explain that knock better or you will get just what you got.

Check the oil.

Maybe the dummy that changed it didn't tighten the filter or plug enough and you lost a bunch of oil.

One time, I paid to have my oil changed. They charged me for the new filter and five quarts of oil. They put on the new filter but didn't add the oil. I did not check the oil before driving away. My engine seized. I sued. They paid for a new engine. Not the same anymore.

Add a quart of transmission fluid to your oil. Drive car for 300 miles. Drain oil and replace with amount of oil manufactured says to with synthetic oil. Drive car. After every 3000 miles change oil using grade of oil you use to use. Before each use, check all fluid levels and air pressure. Driving a car and making it last are not the same

When I got new car, I did above and now, after 400,000 miles I have a knock too. But it is normal.

If you lost enough oil that your engine is regularly knocking, it's probably time to start shopping for a new car, cause yours is toast!

In march I got my oil changed, I've been doing a lot of highway driving since then. My oil light has recently come on and then my car stalled. When I start my car up it makes a slight knock during idling and it gets faster during acceleration. Is my engine done and can I fix it with out putting in the shop