Amsoil is good stuff.  I used it in my 575 hp (dynoed at the rear wheels)
Porsche racecar after blowing up one motor (stock, about 318hp) using Mobil
One.  The Porsche 928 water cooled V8 motor has issues with one of the main
bearings, we think caused by the oil being beaten into a mist by the crank
and starving one bearing.  Amsoil is said to contain an anti-frothing
compound..dunno about that but I got 2 hard seasons of racing from my 'good'
motor after switching away from Mobil one. When running Mobil One, I would
get a quart of oil out of my catch can after each half hour track
session..the catch can was at the cam cover breathers to keep oil from
ending up on the track.  With the switch to Amsoil, I would get maybe a
thimble full per session...
   I also blew up a couple of race motorcycle motors using that Mobil
One...So, while it may be just fine, I had three failures with it which
makes me not use it anymore.  Others in the Porsche world also lost motors
and when queried, revealed the oil was Mobil One..
  I've used the 20w50 racing compound Amsoil...expensive? Yep!  Especially
when my race motor took 14 quarts to change and got a change after every
weekend at the track.
  In my little mouse motor 1.8liter inline VW, I use just a standard
dino-oil...Penz, Havoline, whatever...At about only $300 per used motor,  $5
a qt Amsoil would be a bit silly.  I change my oil often, at like 3-5k miles
or whenever it becomes dark looking on the dipstick.  I will not use Mobil
One, even in a $300 used Rabbit motor or my lawnmower...Again, it may be ok,
but I've lost too many motors with that stuff in them,  I think I've blown
about 6 motors in my long life and 3 were running Mobil One..so I no longer
tempt fate with that stuff.
  Changing your oil often seems to be a good thing to do for your motor's
well being.  I also cut open my oil filter every few oil changes to see if I
find any metal in suspension or trapped in the filter...You can sometimes
save a motor from death if you see from your filter that some adjacent
pieces of metal are not co-existing happily and are scraping bits from each
other..
  Don Hanson