OnePlus 6 battery drains faster after the latest OxygenOS 5.1.8 update5
That's the bad news. On the bright side, it looks like not everyone is affected by this battery drainage bug. There's a huge thread on OnePlus' forum where many OnePlus 6 owners claim their battery is drained faster than normal, but there are also voices saying that they don't see anything unusual in how their phone handles battery energy consumption.
OnePlus has yet to respond to these complaints, but if they prove to be true, there's likely going to be another OxygenOS update released soon that will address this issue.
In the meantime, if you haven't yet updated to OxygenOS 5.1.8 yet, we suggest waiting a bit until OnePlus releases a fix or confirms that the current update is bug-free.