Hello and thank you for choosing Just Answer.
Have the lucas or the oil change made any type of difference in the sounds of the knocking?
What grade fuel are you using?
If the lucas did make a difference that you have a clogged/dirty lifter(s). Lifters shoot up oil and keep the motor lubricated, if you have a clogged or dirty lifter then you will not get enough lubrication. This will cause a knocking noise from the engine. Often times that can be fixed using a engine flush or engine treatment. However if it does not work, then you may need to replace the lifter(s).