The real reason is that you can run at a higher power setting without crossing your tit limit because the exhaust temp is lower on an 8.5:1 engine at the same power setting.

I'm having a hard time on my 7.5:1 getting up to 17+ gph LOP at fl260 without blowing through my tit limit, for example.

The egt is lower and the engine is more efficient with 8.5 CR pistons.  Again I ask for data.  If I am indeed experiencing 5% better performance at 17.5 gph than the norm I do think that is significant and wound like to investigate the reasons further if anyone elso on the list is willing to share data.  As far as FL 260 is concerned I think I would get a nose bleed way up there so I cant provide any help--other than to suggest you descend before your blood boils.

paul