Question 1 - Manual says use premium fuel. Most vehicles which require premium fuel will tolerate regular fuel in a pinch if you cannot get premium fuel for some reason. However, the computer does this with a knock sensor signal which retards engine spark timing so performance and fuel mileage go down the drain. If you try to run on regular permanently you will most likely turn your engine into a very expensive paperweight. Fan noise is likely caused by a bad bearing or the squirrel cage rubbing against the housing.
Replacement is usually the only cure.
If you intend to make this a regular practice you will turn your transmission into a very expensive paperweight. Brakes are a lot cheaper than transmissions. Hi Eric, I just bought a brand new 2001 Honda Civic. We brought it to the dealership and they said it was the catalytic converter. I know very little about cars and I am concerned that they are not telling me the truth.