The substantial improvements were discovered by an unnamed developer who spoke with Softpedia after installing OS X 10.8.1. Previously, the developer's MacBook was reportedly showing a battery life of 4 hours and 5 minutes after a full charge, but installing the beta software increased the advertised battery life to over 8 hours.
The details suggest Apple is working to fix battery life issues that some users have reported since the release of Mountain Lion on the Mac App Store in July. AppleInsider first highlighted earlier this month a number of MacBook Pro and MacBook Air owners who complained of battery performance issues after installing Mountain Lion.
Those complaints were later validated by a series of tests conducted by ArsTechnica. Their unscientific data showed that Apple's new operating system drains batteries significantly faster than its predecessor, OS X 10.7 Lion.
While Apple has not publicly commented on any battery issues with Mountain Lion, a number of users who have posted on Apple's official community forum have said that company representatives reached out to them and obtained system information in an attempt to fix the issue.
Only certain MacBook models have been reported by users to experience the battery drain issue introduced with the launch of Mountain Lion. Some others have said that their battery life actually increased since updating to OS X 10.8.
The first pre-release beta of OS X 10.8.1 was supplied to Apple's developer community earlier this month. Documentation accompanying Build 12B13 revealed it aims to correct a display noise issue when using Thunderbolt, but made no mention of battery life.