Just checking back into this thread....

Chris, almost without exception I default to your very extensive experience and expertise, but we'll have to agree to disagree here...at least for *that* engine.

I adjusted and monitored the tuning on this engine every day over a 2 month period during my daily commute, which is a mix of stop and go, highway, and backroads driving. With that AFR map my car was running <325 deg F temps all day long and I was getting ~28mpg highway. Oil temps never got above 225-230 deg F, that was stop and go in 95 degree summer heat on the highway. So, for *that* engine with its unique combination of components and wear, this fuel map was very effective.

IMO -- the takeaway here is that you can start with some basic guidelines, but it's important to measure what your engine is doing and give it what it wants.

Is your motor turbocharged? Forced-induction cars can benefit from an overly-rich mixture because of the cooling effect of the extra fuel.

In general, though, a 11.5:1 mixture is richer than just about anybody needs. The engine should behave the same or better at 12.5:1. This could be an exception, but it would be unusual for an NA motor need to be that rich.





http://members.rennlist.com/pbanders/PCV.htm


--DD