03 May 12 13:49, Mark Hofmann wrote to Roy Witt:

 RW>> The oil may not be, but the polymer additives they use shrink or
 RW>> expand at 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
 RW>> fire under the engine's oil pan to thin out the oil before they
 RW>> 'hand cranked' the engine to start it. Of course, that was before
 RW>> multi-weight oil was invented.

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

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

I've seen that done in the late model Malibus. It's not that bad of a job.

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

Apparently not.

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

Whatever the owner's manual tells you to use...

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

I could see  using a multigrade oil like 10w-50, but only in South Texas
and the desert south west and only during the summer months. In MD, 10w-30
should be the normal oil to use in summer.

It gets to 100 here for a few hours each day, usually late in the
afternoon. The same for New Mexico, Arizona and California and they're 5
or 6 degrees further north latitude than we are.


                R\%/itt


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