XPost: misc.phone.mobile.iphone, comp.mobile.android   
   From: pmcook@gte.net   
      
   On Fri, 11 Dec 2015 11:22:34 -0500, nospam wrote:   
      
   > in other words, it depends on the engine, just like i said.   
      
   We're reading the same words, but we're interpreting them   
   slightly differently.   
      
   We both agree that a perfectly running engine has the octane   
   rating *designed into* that engine (see also note 1).   
      
   However, what I was intimating was that a *badly* running   
   engine has different octane requirements (e.g., if the   
   cylinder head is so coated with carbon deposits that it   
   appreciably changes the compression ratio, or if the spark   
   timing or valve timing is knocked off spec, or if the EGR   
   system, which is the problematic VANOS in my bimmer, is   
   out of spec, or if the cooling system is blocked, etc.)   
      
   NOTE 1:   
   Even a perfectly running engine might have different octane   
   requirements based on what you're doing, e.g., if you're   
   running at very high rpm towing a trailer up a steep hill   
   at high altitude, etc.   
      
   The knock sensors will prevent damage though, so, it's never   
   as simple as just saying it's the octane rating alone that   
   matters.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)