Many users have not been too happy with Apple’s OS X 10.8 Mountain Lion due to its notorious tendency to quickly drain a MacBook’s battery. There has been some empirical evidence uncovered to support this fact, as Ars Technica recently tested both Mountain Lion and OS X 10.7 Lion on a MacBook Pro to see which operating system drains faster.

Photo credit: Apple

According to the test results, the MacBook Pro’s battery ran out 38 percent faster when Mountain Lion was running.

There were no changes in the settings of the test MacBook, and several tests were run on the device, with various applications opened as part of the testing process. These applications included Google Chrome, Safari, Twitter, Photoshop, Outlook and Mail, with Dropbox and gfxCardStatus running as background apps.

Brightness was at half-strength for purposes of the test. As for connectivity, Wi-Fi was on and Bluetooth was off. All in all, the test notebook was able to operate for an average of eight hours while on OS X Lion, compared to five hours on OS X Mountain Lion. Simply put, it appears as if Lion wasn’t exerting effort on the Nvidia GeForce GT 650M, a part known for its high power consumption.

Jumping into conclusions, though, would be tantamount to dicto simpliciter – a sweeping generalization based on one test and one test alone. Others who posted on the Apple forums claim the CPU tends to heat up even on idle as a result of running Mountain Lion.

TGhere are Mountain Lion features such as Power Nap that have been singled out as the culprit. Ars Technica’s tests may hold some water, but at the end of the day, we can’t use one point of reference when finding the root cause of the battery issues associated with Mountain Lion.

Apple has not yet officially commented on the issue, but if it persists, there’s a chance we’ll hear from them soon.