What is a hydraulic lifter and what does it do?

I have a 92 Nissan Maxima that has been making a diesel like sound. Some people told me its the valves, my mechanic tells me its the hydraulic lifter. I added Lucas Oil treatment 60% to oil and it got rid of the noise for about a week. Its back. Doesnt affect performance but annoying and I need to sell the car. Is there a quick fix? What about Rislone? And would replacing the lifter actually fix it?

You can Google hydraulic valve lifter for yourself to get a more complete explanation than I care to type. I have had good results with CD2 detergent type to quiet noisy lifters. Your have either two or four lifters per cylinder. Replacing one may cost hundreds of dollars so you might be asked to consider replacing all which will cost even more. If you have an overhead cam engine, the cost might be a little less than with a pushrod engine. I have never paid for this kind of work so I can’t say exactly how much it will cost. A little lifter noise is harmless but annoying. Very loud lifter noise can eventually damage your camshaft.

What is a CD2 detergent? Thank you!

It’s an additive you can get at an auto parts store to pour into the engine oil…

thank you - does it compare to Rizlone or Lucas? And of the three, which do you recommend?

I have not tried Rislone or Lucas. All that I can say is that CD@ detergent type has worked for me on more than one car with a noisy lifter. If it works for you, it will be good until you change your oil; then you need another application. Gunk also makes a valve lifter quieting liquid that has worked for me. One may work and the next may not; you have to try something.