Everyone knows that the “upgrade” to OS X Mountain Lion severely reduced the battery life in Mac laptops by up to 38%. And while OS X 10.8.1 helped things some, the fix was still meager compared to the oceans of juice you comparatively got on the same machine running OS X Lion.
OS X 10.8.2, though? Much, much better. In fact, according to The Mac Observer, in the latest Build 12C35 of OS X 10.8.2, not only does the latest development version of Mountain Lion give users a bigger upgrade in battery life than OS X 10.8.0 or OS X 10.8.1, but their test system — a 2011 15-Inch MacBook Pro 2.0GHz i7 — now has more battery life than it did running OS X 10.6.8 Snow Leopard, the previous champ Mac operating system when it came to conserving juice.
In fact, while their test system lost 105.5 and 80.5 minutes of battery life compared to 10.6.8 in OS X 10.8.0 and OS X 10.8.1, respectively, it actually gained eight minutes against OS X 10.6.8 in OS X 10.8.2. Now those are some impressive results. Results I’m now off to test for myself.
Source: Mac Observer