you actually already know the answers to your own questions. If you don't want to use the recommended products for your car, you don't have to. The car will adjust timing for the lower octane, performance will suffer a little but not noticeable to those who don't drive hard often. The great oil, verses the good oil is what it is. If your aren't going to keep it for 100K miles, then use cheap oil. Tires, well, if you aren't going to the track, drive her to the upper limits, then all season radials are a good choice. Go even cheaper, and your handling will suffer, but, using the cheap oil, and cheap gas, you won't be worried about handling anyway. Sounded kind of smug didn't it. Always use the best car products if you really love your car and intend to keep it that way. It really doesn't cost all that much to keep her in top shape. Good luck either way, the car can take it. At least for awhile.