Lately, the ICE has occasionally been vibrating or knocking a bit just before it shuts off. It seems to be more noticeable when the car has just stopped at an intersection. Wondering if anyone else has noticed this. The humidity here is higher than normal for Colorado. The temperature is in the 80s F, so it's not a cold weather issue. Edit: I've been driving through more water than usual due to the recent flooding here. I wonder if that has something to do with it.
My 2011 has 41k and has not changed how smooth it feels since new, when the ice shuts down or starts up. I can tell you what I do and it's only personal preference with no evidence that it helps at all. I switch back and forth on tank fill ups from high 93 to medium gas octanes. Ever since the rattle shaking engine start-up issue was discovered a while back. I also add Heet during the colder months of the year. This seems to help keep the cold start-up issue away and I have not noticed any extra vibrations on the ice start or shutdowns, IMO. I also prefer what is called the higher tier fuel stations. Maybe a video of how it shakes. Maybe if it's bad you can show a close up of a glass of water vibrating on shut down. If you can't record it maybe it's normal. my2cents.