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?