My owners manual says if temps are to remain above 0F and expected temps to 100F, use 5 or 10w30. If you go to the Hyundai hmaservice site, it says if temps over 100F, 10w40 would be appropriate. I called both the dealer and the 800 customer service number to ask why the difference and which one to use. Temps will be 110+F on my travels, so it is a honest question, not just being nit-picky. Both said they don't know why the difference, just use 10w30 since its in the manual. My concern is that in this small 2.0L 4cyl, high revs and high temps may need the 10w40 for proper protection and I won't be using it. I'll be doing some light off-roading which makes it worse with less airflow. Hyundai should have been able to give me an answer.