RW> If you're using a multi-weight oil, think viscosity. i.e. with 10w-30,   
   RW> think of the 10w viscosity as winter flow. Today's multi-weight oils are   
   RW> tested for flow at controlled tempuratures, the 10w meaning that the oil   
   RW> will flow like a 10 weight oil at a cold temp such as is encountered in   
   RW> the winter time.   
   RW>    
   RW> The 30 in that nomenclature means that the oil will flow (viscosity) like   
   RW> a 30 weight oil at a higher temp. So, the warmer 10w-30 oil gets, the   
   RW> closer to the viscosity of a 30 weight oil, rather than that of a 10   
   RW> weight oil.   
   RW>    
   RW> When you park the car overnight, the warm engine temp will keep that   
   RW> leaky lifter from leaking down for a longer period of time, hopefully   
   RW> keeping its 30 weight or heavier viscosity longer. If its a garage kept   
   RW> vehicle, it may not get cold enough to thin out the viscosity and keep   
   RW> the   
   RW> lifter pumped.   
      
   So the oil is actually thicker at hot temperatures or when it is hot outside   
   if you are using a 10w 30?  10w for cold and 30 for hot?   
      
   The only pattern I have noticed is that I don't get as much (if any) lifter   
   noise when it is warm/hot outside or when the engine has not been sitting for   
   a long period of time (overnight).     
      
   I had tried adding some of that Lucas Oil "Heavy Duty Oil Stabilizer" (which   
   is a really thick consistancy) last summer and it seemed to make the problem   
   worse.  I did another oil change shortly afterwards and tried the synthetic   
   10w30.     
      
   - Mark   
      
   --- WWIVToss v.1.50    
    * Origin:  http://www.weather-station.org * Bel Air, MD -USA (1:261/1304.0)