The first number (the "5" in 5w30) is only a relative number which basically indicates how easily it will
allow an engine to "turn over" at low temperatures. It is NOT a viscosity reference. In other words, a
10w30 is NOT a 10 weight oil in cold temperatures and a 30 weight oil in warm temperatures.
In fact, since SAE viscosity classifications only apply to an oil at 100 degrees C, it doesn't even make
sense to label it as a certain SAE viscosity at any temperature other than 100 degrees C.
Besides, if you thought about it for a second, it wouldn't make sense for a 10w30 oil to be a 10 weight
oil in the cold and a 30 weight oil in warm temperatures. What liquid do you know of that gets "thicker"
as its temperature increases or "thinner" as the temperature decreases?
Not to sound rude, but you should also do some reading on your own before criticising other peoples' information. Your statements on viscosity are not accurate and several of your comments contradict themselves.You really need to do a little more research on oil technology and how oils are rated and by whom.
You should be okay in Texas, cold starts should be rare for you, but there probably won't be a diffrence. I'd stick to 0W-40
I'm familiar with Dr Haas and his writings about oil. He should be read carefully.
The information came directly from this document: http://www.zag.si/~jank/public/bmw/oil_bible.pdfPadawan, thanks for clarifying what you are referring to. The information you quoted is incorrect or taken out of context, however. Where is it from?