Regular gas is dirtier than premium? You’ve bought the Kool aid.
Not the fuel itself. But if the car calls for premium and you run regular, the car pulls timing and you might have a less complete burn...which could mean more deposits left in the combustion chamber. Plus it might run hotter, shorten the life of the spark plug...which also further could result in less efficient burn and deposits. But that's not terribly likely these days...unless you're turbo or towing a load.
But in an of itself...you're right. Both regular and premium contain detergents and neither is "dirtier" than the other.
I would say most Sienna, Highlander, Camry V6, and Avalons have never seen a lick of premium fuel in its entire life and a lot of the older ones are reaching 400,000 km no problem.
This. Lots of 3MZ-FE engines out there with very high mileage that haven't had a drop of anything other than 87 octane in them and they're fine. The engine was designed to run reliably on regular fuel as it simply advances the timing to the point of whatever octane you're running. I ran a few tanks of premium, made no difference to feel or fuel economy.
This idea that 91 octane is "better" than 87 is a myth. It's just more resistant to detonation. Octane is not BTU. A liter of gasoline contains about 32,000 BTUs, regardless of octane rating. The performance of your engine, including economy, is dependent on a large number of variables. Even advancing the timing might not result in any gains thanks to combustion chamber shape, valve timing, cam profiles, and on and on.
I like to treat my cars right. I use premium synthetic oil, top tier oil filters, quality parts and so on. But, in a lot of cases, the 20% premium for premium is wasted money. If your manual calls for premium, use it.