Hmmm! There is some complete drivel posted in here.
Show me any other engine that can match the IO520 in my Bonanza for the combination of proven reliability, power to weight ratio, cost effectiveness, fuel economy at or below 10,000' over 500 nm - apart from a similar Continental or Lycoming!
My V35B trues 160 kts at 10,000' on 48 L/hr. There is no doubt I could get that back to 45 L/hr if I had an all cylinder engine monitor and ran LOP.
There is a very good reason they are still putting them in new aircraft.
Sure, FADEC would be nice but when the price is reasonable and the reliability is there.
Dr 