Others might beg to differ, but in my experience...
Mash temperature has negligible effect on efficiency. Ditto for mash time. Ditto for water to grain ratio (i.e., qts/lb). If you mash in some water at 148 to 154 F for 40+ minutes, you're going to make beer at an efficiency that is mostly affected only by the extent of the crush. Beyond the crush, very little matters.
My experience. YMMV... but I doubt it.