They do push Red Line but they also used to be OK with Amsoil. It makes good sense that they try to get everyone running Red Line. When engines come in for service it's good to have that base line. I used to have a DA 150 S/N 257. During its lifetime it was run on no less then 6 different brands of oil. It saw life on 4 different airplanes. I estimate that when it hit the ground it had over 2,000 flights on it. Like I said earlier, pick a brand that is easy to get, use the correct ratio and it's a non issue.