The latest update size is around 1.6GB (1609MB) and you can it via OTA update. But this update is currently available to some of the s as a beta update.
Oxygen OS 5.1.4 update Changelog:
1. System
- Updated Android security patch to July 1, 2018
- Added sleep standby battery optimization (Settings -> Battery -> Battery optimization -> Advanced optimization -> Sleep standby optimization)
2. Camera
- Improved photo clarity
3. Message
- Added Group Messaging
4. Gallery
- General bug fixes
Note – OnePlus have introduced the sleep standby battery optimization feature in this version of Oxygen OS, which should help the s to get more battery juice for a full day.
Go to Settings > Battery > battery optimization > tap on the three dots > select Advanced optimization > choose ‘Sleep Standby optimization’.
Read More: Android P Beta Developer Preview 3 is now available for OnePlus 6
When this setting is turned on, the system will intelligently identify the s’ sleep pattern based on the phone usage. Then the handset will automatically be turned off the network during the specific periods of time to reduce the power consumption. Even the phone sleep mode will automatically be turned off in the morning to notify all the notifications during sleep mode.
Please Note – The update will be available to some of the specific s and will be rolled out globally within a few days after fixing all the bugs. So the VPN service won’t work until the official OTA released for everyone, because it isn’t based for region specific. If in case you’re facing any issues or want to ask something else, you can always put your here.