I usually change the oil between 4,000-6000mi. (70 percent highway miles) Synthetic oil will be changed at the 6,000-mile interval. I am trying something new. I was originally going to use Shell Rotella T6 but I can’t find any. So, I am trying the diesel oil form Mobil one. I am not sure if I am throwing money away, but I am hoping to go up to 8,000 mi because I assume the diesel oil has more additives for wear and tear. I want to know your knowledge and opinion if 8,000mi intervals is a bad idea. I know some people use 5w20 on some years, but I think those engines burn a bit of oil. Heck I dont mind using 5w30 cheap oil if it can make it 5,000 miles.