Question, I was out flying my Avistar yesterday, and I noticed that the engine was vibrating quite a bit, I am sure it was much more than it has in the past. I thought the glow starter was going to fall off when I started it, it was rattling so hard at the end. I took it home and the prop and spinner looked alright, the mounts were tight to the firewall (although I tried to tighten it more and broke the screw off, so I took a couple steps backwards) the only other thing I can think of is I had mounted the engine to the mount with threaded screws, rather than a screw, washer, nut. (I am changing that). Could that have caused such vibration? Also, since I haven't spent a lot of time around other planes, do you guys get much vibration in the engine, when it is mounted properly? Or is it real smooth?

Also, I still get mixed responses to quality and age of fuel. Could some of the roughness be due to using old fuel? Seems some guys say it stays good a long time, and others say trash it at the end of the season. I have about a quarter gallon of some fuel left that I bought late last fall. It sat out in the garage all winter in Wisconsin, too.

Thanks in advance for your thoughts!!