I used mid-grade as Triumph recommended for the first few years. Changed to hi-grade after the BB kit was added. It seems to get marginally better MPG. I suppose with a 10:1 compression ratio, it's kind of iffy between mid and hi. Before the BB, I could get by with regular occasionally, but it doesn't run well on it now. One of the reasons may be the 10% ethanol I can't avoid now. Can find any local stations that sell non ethanol fuel. Got some in NC and noticed I got 10% better fuel economy riding through mountains!
