While I understand what you guys are saying about turbo cool down time, you have to remember a couple of things.
1) The Turbo chargers now a days are not only oil cooled, but Water cooled as well, so they never really get Hot like they used to. You never see them Glowing Red. I mean, I have had my Evo on the dyno for 6 hrs at WOT and the turbo never got glowing red or anything close to that. Oil temps went up during this process though.
2) This is a stock Hyundai 2.0 that is basically a "de tuned" Lancer Evo X motor. This particualr Hyundai Motor shares many components with the Evo X 4B11T motor. If a 5w30 Synthetic is all the Evo X gets from OEM and it makes more power, and more boost than the Hyundai then a 40w is kinda overkill IMO for this car. BUT it is Direct Injected, and runs a much smaller oil cooler and Intercooler. Thus, Hyundai is possibly utilizing a 40w to make up for the lower cooling capacity? A good upgrade for this Hyundai if driven hard would be a Oil Cooler upgrade IMO.
I like the Sonata Turbo, I think its a great car. Making that much power out of a 2.0 while running 87 octane is astonishing. The Evo X still requires premium since it EFI not DFI type fuel system. According to my sources, the Evo X was going to go to direct ignition for emission reasons, but Mits just cut the Evo off all together and is discontinued in 2012. Downside to DFI is tough to find upgraded injectors to handle more power and is a hint to why the Evo X came with EFI, since its intent was for racing purposes.
Anyway, sorry to get off subject. Great Car, Should treat you good for many years to come.
Jeff