more on oil (viscosity)

["Robert W. Murphy" <rmurphy@domain.elided>]

I really don't want to drag this on longer, but I have a question regarding 
multi-viscosity oils, which might interest others.  If I am correct, 
multi-viscosity oils are for multiple temperature ranges.  The first number 
(10, from 10W30) represents the weight of the oil at the lower temp range and 
the second number represents the weight at the higher temp range.  Is this 
correct?  So, hypothetically, at -10 degrees F the oil is as thin as 10W oil 
and at 100 degrees F the oil is as thick as 30W oil.   What about in-between 
temps?  Would the oil be like a 20W oil at 30 degrees F?  Also, if one lives 
where the temp rarely drops below 40 degrees F (Miami) and a vehicle calls for 
10W30 for temps between -20 F and 100+ F, would it be wise to run just 
straight 30W oil?  Is there a need for the multi-viscosity oil since the temp 
is always warm? 

Just wondering?

Rob Murphy
90 Spider
Coral SPrings, FL

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