/sci/ - Science & Math

Where can I find information about Falcon 9/heavy's upper stage variant for long duration coasts? I know they can be identified by their gray band of insulation paint, but i've heard somewhere that there's more differences than just that.
I'm trying to track down the specific source that said that there was more equipment onboard that kept the RP-1 thermally stable, it was some autistic "Gunters Space Page" tier website, but iv'e had no luck in finding it.
I looked through the Falcon user guides for it too, but theres no mention of it anywhere. Any articles that mention it are just that... mentions.