[10/10ths]

…..and all modern cars have knock sensors and can run 87 octane unless you see a label on the fuel filler cap that says, “MUST” use a specific octane.

If it is just a “recommended” label, then you are fine with 87.

Now, that part of it is just the knock and damaging engine part of it.

The detergent part of it is less exact. Many companies only put their best fuel additives in their premium fuel.

But, you can fill up on 87 and drop a bottle of Techron or Red Line or Driven fuel injector cleaner in the tank and you will be fine.

Of course, that brings the cost up to just buying premium fuel.

Don’t overthink it.