I usually use Mobil Super+, which is 93 octane. Once in a while, I'll throw some Sunoco Ultra94 octane in there, just to mix things up a bit. I've found a few Sunoco stations that sometimes sell Ultra94 for less than Mobil Super+.
When I first got my CSVT, I was using 93 octane from Hess, but after I switched over to Mobil Super+ I noticed that it seemed to run a bit smoother, and gas mileage went up slightly.
