I own a 2013 Genesis sedan with the 3.8. I bought it with 40,000 miles as a lease return. It now has 129,000 miles. At about 90,000 miles, it began to run rough and stall at intersections or on a sharp corner. I took it to my trusted mechanic shop and he had the answer within 30 minutes. He told me these engines are VERY touchy with how you change your oil and what oil you use. I have always used Royal Purple full synthetic with their oil filters on all my cars. They don't make one for our engines so I used what I thought was a good
aftermarket filter (I don't remember the brand now). The shop owner said you have to use only OEM filters and when using synthetic, you can't go 12,000 miles between changes like all synthetics say you can. He said there are not enough detergents in synthetics to keep the engine clean enough. He had the same thing happen to a customer's KIA with the same engine. He told me what happened was the variable cam actuators get gummed up and can't work properly under certain conditions and the engine dies. The only two choices for a fix are a top end removal to reach the actuators and replace them, or use only OEM filters, change the oil every 5,000 miles with a good quality non synthetic oil and add a quart of Marvel Mystery oil. I thought after I did a couple of oil changes, the Mystery oil would have cleaned out the gunk so I wouldn't have to use it anymore, so after the second change, I used all oil. It started dying on me again just like it did before, so I took it back to him. He said I would have to use the Mystery oil every oil change from now on. I speak from personal experience, that with these engines, it does matter which oil and filter you use and how often you change them. I've never had any other problems with the car.
