1) Does it matter what brand you buy?

Not really. They all get their gas from the same refinery, so there's really no difference. As long as there's no water in it, gas is gas.


2) Does it really matter what kind you buy...as in 86, 88, 91???

That depends on the octane needs of your car. As a rule, the lowest octane gas that doesn't cause detonation is best. The cheaper, lower octane gas will actually work better. Octane has nothing to do with quality, BTW.