[EL'ation]

QUOTE (osrk @ May 11 2010, 03:05 PM) index.php?act=findpost&pid=321811

My first oil change is coming up. The hyundai manual recommends that you use 5w-20 but says if not available you can use 5w-30 too. I think that 5w-30 is the way to go. 5w-20 is way to thin. Look at the data sheets at the end of these pages and compare them

5w-20
http://www.amsoil.com/storefront/xlm.aspx
5w-30
http://www.amsoil.com/storefront/asl.aspx

The 5w-30 is stated to last 25,000 miles while the 5w-20 is only stated to last about 7500 miles. I think 5w-20 is way to thin to provide protection and is sacrificing engine wear for a 1% increase in mpgs. Particularly important I think for a GDI engine is the Noack Volatility test, the 5w-30 is ~30% better vaporizing a lot less oil. Hyundai gives you the choice in the owners manual and I do not think the minuscule boost in mpgs is worth the engine damage or wear.

What do you guys think?

Amsoil 5W-20 is formulated differently than its 5w-30. The life expectancy has nothing to do with the viscosity of oil.
Those two oils are in two different classes.

5W-20 was created for better gas mileage originally for cars that take 5W-30. And it saved tax for manufacturers in the US (CAFE). It of course caused more wear to the engine.
But I don't know that applies to the Sonata since they may have developed the engine around 5W-20. That case, 5W-30 would be too thick.

I would look into Korean owner's manual and see what is recommended there. They don't have the CAFE law, so they would recommend what's best for the engine.