And what type of gas do you use..

Never, Sheetz or Sunonco

whenever i get below a quarter tank...

i use whatever is close and/or convenient, unless it is at a lower level than the surrounding area, due to some stations having water in their tanks. the station i frequent most is a 7/11 that has sunoco.

All the gas stations around here seem generic, usually go to bp by work and get 93

I fill up once a week, or when it hits 1/4 tank.
I live on the border of NC/SC so I will hop the border and fill up at a Exxon in SC and save about 20 cents a gallon.

If I were to drive farther into the state its even cheaper, but not cost effective.

About every 10 days - Shell 87 octane

About once every 10 days or so. 93 SUNOCO or BP.

I only use Shell or Chevron Premium Octane. If I can find Ethanol free gas then I get it. I fill up on average every 5 - 6 days.

Once a weekish

there's a shell station that's a block out of my way home that does premium for mid on mondays, when I think about it I'll stop and top off the tank otherwise ever 1.5 - 2 weeks.

Shell Premium, every week and a half or less. Miss the V6 and every 2 weeks... but love the power.