For the Hyundai, either the 5W or 10 W should work just fine. For your 3800 engine, I would go with a 10W-30 weight even if you went to platinum versus ultra platinum. The 3800 series engine is very forgiving when it comes to “most “motor oils. However, in my own personal, anecdotal experience, some 5W-30 weight oils (Valvoline and Napa synthetics) allowed a rattling sound to come from my 3800 engine, But 10W30 weight oils do not. I think this engine prefers higher viscosity lubricants. However,, there may be some brands where a higher HTHS might allow a 5W-30 to run happily in a 3800. Castrol perhaps? YMMV