RW> The oil may not be, but the polymer additives they use shrink or expand
RW> at
RW> those temps changing the viscosity along the way.
RW> 
RW> As you suggest, pure engine oil will thin out at higher temps.
RW> 
RW> I can varify that by a story my dad used to tell about his earliest
RW> experiences with cars in the 1920s. In the winter they would build a fire
RW> under the engine's oil pan to thin out the oil before they 'hand cranked'
RW> the engine to start it. Of course, that was before multi-weight oil was
RW> invented.

Interesting..  I didn't know about the polymer additives that effect the
viscosity in different temperatures.

I scheduled to take my Monte Carlo back to the engine shop because there
appears to be a small leak somewhere around the oil pan gasket.  I wouldn't
normally be concerned, but it is still under warranty for 2 more years.  If
that gasket needs to be replaced, that is a pain!  You have to drop the
sub-frame!

While I had them on the phone, I ran the lifter tap (on cold start)
question by them.  He said not to worry about it unless you hear that noise
all the time while driving.  Under a minute of tap on warm up on those
engines appears to not be unusual.

He didn't think that changing the oil types would make a difference and
said to stay with 5w-30 (I have always used 10w-30).  

I believe it is worth trying 10w-40 or 5w-40 - as I really don't see that
causing any problems.

- Mark

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