I will start with vehicle maintenance is not at the top of my list. I use my vehicle for work, sales rep for a foodservice company. Sometimes needing to haul product for my customers using dry ice to keep frozen items frozen and refrigerator items chilled. So my goal/break even point in my eyes is 200,000 miles. That is the point where my mileage reimbursement gets close to my vehicle expenses. Not a perfect science, but I feel any car with more miles than that is just waiting to strand you on the side of the road or nickel and dime you to death. And being stranded with $700 of beef tenderloin in the back would make me very anxious.
So to answer your questions, I use 87 octane fuel. About 30 gallons per week. Main fuel companies are Murphy USA, Phillips 66, Casey's, QT, and Shell in that order. I have not used any additives.
As for oil change interval. I do it myself approximately every 7500 miles, which is about every 5-6 weeks. I use 0w20 oil from rural King. It is a synthetic oil that runs about $13 for 5 quarts. Oil filters are fram, and Mobil. I like the way the fram sit on the bottom of the engine, so planning to switch back to them on next oil change.
Tires. I got 75,000 miles off my first set. I did not rotate, align or balance them the life of the tires. They were in pretty rough shape when I replaced them. The second set of tires lasted me to the 133,000 mark. I replaced the front tires when threads started to show. I still have the second set of tires on the back and plan to replace them in a week or two. The tires are Michelin just like what came on the car.
Clutch fluid is original. Nothing done in regards to this.
Hybrid drive belts. Didn't know such a thing existed. So those are original.