I read an interview with the/an tuner for HSV and the question of lean cruise came up, his answer was that they did not consider that it was a priority for their customers. He also mentioned tip in response.
Unfortunatly I can't find the article, I pinched the magazine from the huge pile in the son's room.
Corvette probably has a similar market position.
As for Diesels they produce huge levels of NOx, which has been why in Australia at least until very recently they did not bother to measure it.
As for the Cessna link these motors are at around 65% load and they are running turbos (mainly to compensate for altitude). When I cruise I am using 20% or less load, at around 2000rpm. Very hard to burn a piston or valve like this, if in doubt check the EGT map I posted up earlier in this thread.
If it was bad for the motor, Holden would not have used it for years.
But perhaps F**d would have
Cheers, Steve