Elantra Motor Oil Query

I recently bought a 2006 Elantra GLS, and the recommended oil in the Owner's Manual is 5W-20, with 5W-30 and 10W-30 listed as acceptable substitutes depending upon ambient air temperatures. Now, I know all of
the previous discussions regarding the pro's and con's of each viscosity, but I find the information on Hyundai's Service Website, www.hmaservice.com, quite confusing, if not downright wrong.
In viewing the Shop Manual for the 2006 Elantra, a graph shows that 5W-20 is the recommended oil for ambient air temps of greater than +40 degrees C, to lower than -18 degrees C. In fact, the caption for the bar graph for 5W-20 states: "5W-20 is recommended regardless of environment." The graph also shows 10W-30 as being acceptable at different ambient air temps. Strangely, it does not even list 5W-30 as an alternative.
Now is where it gets interesting. In looking at the same section of the online Shop Manual for the 2005 Elantra w/CVVT, here is what it says: 5W-20 is only recommended for ambient air temps of below -10 degrees C. The bar graph caption includes two disclaimers: 1). Restricted by driving condition and environment, and 2). Not recommended for sustained high speed vehicle operation. The graph shows that 10W-30 weight oil is the best recommendation for +40 degrees C to -25 degrees C air temp operation.
Surely, the Elantra's engine didn't change tolerances or metallurgy between 2005 and 2006, nor did 5W-20 motor oil improve that drastically in one year.
I've heard that the 5W-20 oil recommendation is used primarily to help attain the government's-manadated CAFE ratings for testing by all of the manufacturers. But, something is very strange with Hyundai's Owner's Manual recommendation vs. their online Shop Manual data.
Any thoughts?
As an interesting observation, I have a Dodge Grand Caravan ES with over 158K miles that's used 5W-30 its entire life with an oil change interval of 3K or 3 Months, and it uses about a quart every 3K. On the other hand, I also have two classic SAAB 900's, each of which has over 150K miles, and neither use any oil between changes (same change interval). The SAABs always used 10W-30 dino oil. Is it the difference in the oil viscosity, or just a manufacturing tolerance or metallurgical difference - or, just coincidence?? 5W-X oils use a 5W base stock, whereas 10W-X oils use a higher viscosity 10W base stock. Again, any thoughts on this as well?
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I've been using 5W-30 synthetic and changing it at the required 7500 mile intervals. It works fine. The differences between 5W-20 and 5W-30 are negligible at the lower end of the viscosity scale, so I doubt that there's any significant fuel savings when using the former. I suspect that Hyundai has just found that 5W-20 works well after years of testing it. They also recommend it in the new Sonata 6 cylinder, so perhaps they're also trying to standardize on one oil that will work with their entire fleet.
You're not going to hurt your Elantra by running 5W-whatever in it. I would avoid heavier (10W) oils unless you live in a very warm environment.
OTOH, 0W oil might offer an advantage in fuel economy. IIRC, 0W-40 is the defacto standard oil in Europe these days. If I could find it at a decent price, I'd try it, but all I've seen in Mobil 1 in quarts for ~$5 each.
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