The Editor experiences performance drops even in the default basic level when left alone running. I experienced them every ~3 seconds. My graph didn't show the drops very clearly so the fps counter was how I verified ~15 frame drops.
This wasn't happening in 4.23.1.
Found in 4.24.1 CL#10757647
Reproduced in 4.25 Main CL#10870012
1. Create an empty basic code template project,
2. Open a default level (File->New Level->Default).
3. Run 'Stat UnitGraph' in the console.
4. Run 'Stat fps' in the console.
Results: The Editor has periodic performance dips every ~3 seconds.
Expected: The Editor doesn't have periodic performance dips when just using a basic scene.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-86170 in the post.