Will updating the kernel reset the phone memory? I updated my OnePlus One phone to the company-owned system, Oxygen OS. The battery now is miserable - it depletes within 5 hours. I am looking for a solution to fix that without wiping and reinstalling another OS. I read that installing a different kernel can solve such an issue. I flashed many ROMs on many devices previously, but never updated a kernel. What I will lose if I did it?  What is the best way to update the kernel?
If you're directly writing the kernel with fastboot then it shouldn't touch the user data.  If you're flashing it through recovery it should also be OK, but it's possible for the update.zip file to perform other actions that could wipe data.