I purchased a used 2022 Equinox LS 1.5 Turbo in January 2024 that had 24.4K mile and currently it has approximately 25.5K miles. I use SeaFoam in my 95 S10 pickup with no issues, and it's got over 190K. Would using SeaFoam in the gas tank be beneficial or harmful for my Equinox?
GM does not recommend using any type of additive except for the one they sell. I certainly would not use one if you are not currently observing an issue.
If you do use an additive, GM makes one they recommend that is listed in the owners manual. However, in my opinion any PEA containing fuel system cleaner like Chevron Techron or GUMOUT will work
if you are experiencing engine issues. I would not use Seafoam.
My recommendation is the best thing you can do for your vehicle is run Top Tier fuel, which is fuel that contains additional detergents beyond the EPA minimals which were designed back before GDI engines existed. This is covered in the owners manual. The reason for this is long ago with pre-GDI engines, intake valves were 'washed' by incoming fuel/air charge and gas being a solvent kept the intake valves clean. Now with GDI no longer alowing the intake valves to be continuously cleaned, the increased detergents in fuels is really needed but the EPA simply hasn't kept up. So manufactuers created their own additive packages and call it Top Tier certified.
AAA conducted a study a few years ago and concluded the claims made by manufacturers to use Top Tier (many more than just GM) are accurate and that is does reduce deposits left on intake valves and other engine components. You can start using Top Tier at any time and it will help remove existing deposits. It's basically like you are running a fuel system cleaner through your car without pouring in a bottle each fill up.
Here is a list of the Top Tier fuel brands.
https://www.toptiergas.com/gasoline-brands/ - Keep in mind, regardless of the marketing of the brands (like Shell for example) all octane ratings of fuel at Top Tier certified vendors contain the additional cleaners. So you can use 87 octane as called for by the vehicle and get the benefit. Some companies may have additional additives in their premium fuel but that is above and beyond even Top Tier standards.