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QUOTE (osrk @ May 11 2010, 02:05 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?

Depending on your winters, I agree 5w20 is thin, and possibly compromises maximum protection in hot weather. I suppose the
water-thin oil is recommended to help fleet gas mileage.

On the other hand, 25000 mile oil is over kill if you change it at 7500mi, the maximum change interval for normal service.