Larry, I have been using Mobil 1 15w-50 in my '90 420SEL with 160,000 miles - I was using Mobil 1 10w-30 after I bought the car because I didn't like the Valvoline product they used in the car previosly. I now know that it was not a recommended oil (but didn't know it at the time). I have a little tick which has decreased since changing oil - but is loud sometimes on startup when it is cold. My question is this - can I use the Chevron Delo 15w-40 to see if that will clear up "the tick"? Will switching back to dino oil cause problems? The engine runs great on synthetic and I have no leaks but it is not as quiet as it once was.
I know this has been discussed before but I really respect and trust your advice.
Sorry to hijack the thread.