I started a new job in October and bought a 2018 MacBook Pro to celebrate. Purchased the 13" Touchbar with (mostly) maxed out components: 2.7GHz i7, 16GB RAM, and 1TB SSD. It's a huge step up from my late-2013 model; ~6x according to Moore's Law.

As soon as I opened the box, I upgrade from High Sierra to Mojave. That was my big mistake. I lost a week of productivity setting up the machine and then troubleshooting battery issues: my week-old MacBook was constantly working with the fan on. I was only able to squeeze 2-3 hours of battery for each full charge; well below the 10 hours promised in Apple marketing, which we all know is 5-8 hours in developer time.

Was the problem Mojave? Was it my battery? Posts on Apple Forums and Reddit pointed the finger at Mojave, but I couldn't confirm because Apple makes it hard to downgrade the OS. I waved the white flag and set up a Genius Bar appointment. While backing up my data, I found an article on the Apple Support site titled: How to upgrade to macOS High Sierra.

A better title would be: "How to downgrade to macOS High Sierra". I followed the instructions and a few hours later all my problems were gone. Hallelujah!

Guides

These guides are hidden on the Apple Support Site and you have to read the fine print before it all makes sense:

macOS High Sierra won't install on top of a later version of macOS, but you can erase your disk first or install on another disk.

Downgrade to:

• macOS 10.14: Mojave
• macOS 10.13: High Sierra
• macOS 10.12: Sierra
• OS X 10.11: El Capitan

I recommend reading the guide for the OS you want to downgrade before proceeding to the next section. Basic idea: format your OS partition and download the OS your Mac came with (or the closest version available).

Steps

1. Back up files to another machine, an external hard drive, or a separate partition. I used rsync to transfer files to my old MBP before staring the process
2. Start machine while holding down Command (⌘)-R to enter Recovery Mode
3. Use Disk Utility to erase your current partition
4. Shut down the machine
5. Boot machine while hold down Shift-Option-Command (⌘)-R

The last step will have you enter in WiFi credentials that will be used to download the version of macOS / OS X that came pre-installed, or the closest version still available.

Hope this helps others who are looking to downgrade the OS on their Mac.

Mojave Review

This leads me to my review of macOS Mojave.

I like it. I like it a lot. Dark Mode is the best mode. Shockingly, I am not a fan of how Mojave drains my battery; it's a bit of a deal breaker.

Gonna see how the Mojave patch will fix things before I decide to upgrade. This time I won't forget to backup via Time Machine, it's just the smart thing to do.

Learned my lesson by being Apple's guinea pig and upgrading without a patch release. Never again.