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

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