Re: Knock getting worse
OIL is oil. As long as you have it and its clean no big thing. Thin oil is more myth in my book than film strength which is important at high revs.
Get a stethescope or use a screwdriver and touch the motor with it and listen with your ear.
Is it on one side or in center of engine? Front or back?
Listen to the engine like your would listen to a train track to hear a DISTANT train. You can get LOADS of info with a screwdriver or other listening tool.
Sounds like a lifter or valve train to me, that would be on one side of the motor. Check it out and let us know.
Woody