What is everyone running in their 4 cylinder Sonata or Optima? My 2010 Optima's owner manual allows for 5w20 through 10w30. However, the oil fill cap says 5w20. My current fill is M1 5w20 for the winter time and I plan on running it between 5K and 7.5K and then sending a sample off to the Stoners. M1 was not my first choice and I actually wanted some QSUD but the M1 was free. I am basing my oil choice on price only for this engine. It seems to run good on just about anything. My trips are generally VERY short with a 2.2 mile trip to work and then back each day. It does see some cross town trips and highway trips to keep the oil moisture free. I am running 5w20 because of my short trips and winter temperatures. However, I think come spring I will flip a coin to see if I will run MC 5w20 or some QSUD 5w30. The MC 5w20 is up in price enough that the QSUD is a nice upgrade for essentially nothing ($18 vs $19).