He'* assuming a head gasket/valve leak. Listen very carefully:
A compression check will NOT detect this leak. It'* leaking in way up by your throttle body, and coming in with the intake AIR charge. Have you been losing coolant? Does your exhaust smell like burning coolant? Is your oil milky? Look through the oil fill port. It may not show yet.
Is there coolant in the #4 cylinder? Does the plug smell like it?
Frankly, I wouldn't waste my time with a compression check. It'll tell you next to nothing on these motors. We don't blow head gaskets or valve seals. Those are basically the only two things that will tell you, other than ring/cylinder wall wear on very high mileage motors.
Did you drain your oil yet?