Another Attempt To Answer The Original Question...
From: National Oil & Lube News, December 2000
"Synthetic motor oils have a significantly lower pour points and better cold cranking capabilities than petroleum based products. The cold weather performance of synthetic motor oils and lubricants is probably the most recognizable feature of these high tech lubes. Long after petroleum oils have solidified, premium synthetics continue to flow. Some synthetics on the market have a pour point of sixty and seventy below zero."
Does that answer your question? You see, it's not so much intentional, as it is a natural phenomenon. You can't compare a synthetic with petroluem in this regard despite the coincidental fact that they both have motor oils rated at 10W30. And the W isn't for "weight", it's for "winter"...
And as regards apb's comments. Is 10W30 what your owner's manual recommends for the climate in Texas? If I were located in a hot summer climate like Texas has, I would run 15W50. In fact, for the relatively mild climate of Northern California, my owner's manual suggests that 10W30 isn't sufficient for my car, and instead, it specifies using a 15W50 oil.
In fact, the chart that is located in the technical data section in my manual shows 10W30 is for use in temperatures ranging from -4°F to +50°F. 15W50 is used from +23°F to above +86°F. For year-round use, it specifies 10W40 or 10W50. It does not specify a single viscosity oil at all.
"We drive into the future using only our rearview mirror."
- Marshall McLuhan -
Northern California Wine Country...
"Turbos whistle, grapes wine..."