Chrysler Repair: about oil, tappet noise, hydraulic lifters

Question
hey roland hows it going im sorry to bug u lol but i put 10w30 in my blazer and it started to tick and i was running 5 w30 but what im getting to is i talked to other people about the ticking in the dodge neon with a 2.0 engine and some said that thicker oil will make it beter and some say thiner will help it can you explain how oil make a difference and anything else about oil and older engines and thank you again roland cause you always explain in good detail  

Answer
Hi Derek,
The tappet noise can be caused by hydraulic lifters in which the oil pressure has not built up sufficiently to expand the adjuster to fill the gap between the rocker and the valve tip. Usually if the engine oil passagesways are not occluded (closed down from normal by sludge), then using a thicker oil causes the oil pressure leaving the pump and reaching the adjuster to be higher so the adjuster will expand more and reduce the gap. However, if the passageways are cruddy you can improve that impedement by using a thinner oil or a solvent to remove the crud which subsequently would cause the pressure to be higher down stream from a formerly occluded area where the flow was so impaired that it could not supply oil in sufficient volume to pump up the adjuster or it may more rapidly fill the adjuster as much as it can which makes it quieter initially upon start up but maybe not as quiet later when the thicker oil has completed its ability to pressurize the adjuster to a higher pressure. So I suspect that is why you can get two answers to the impact of viscosity modification of tappet noise. It may depend upon the condition of the oil passageways at that time as far as how clean and open they are to the flow.
I am not an expert in this area, but that is my understanding of it. Because you have two engines you may be able to experiment with both and just exchange oil between the two to observe the effect of weight on noise.
Roland