The web site posted lists the Dielectric Constants for most gasolines.
C-16 is a sort of "standard" in that it comes in on the meter darn close to 0.0, pretty much no sweat when the old rule called for DC's less than 2.3
But now if you go down to Circle K or 76 and buy 91 octane, it will read between 5.5 and 7.0+/-. What? You can't run pump gas as "gas"? So in mid stream last year the D/C limit was bumped to 6.0 to allow for "modern" gasolines.
Because many pump gasolines were still outside the limit, and because of some questioning by some of us who want to run "hotter" gasolines and the difficulty in establishing just what exactly is a "gasoline", the rules committee met, and after some long discussions with Rick Gold of ERC, decided that in the future, gasoline was anything with a D.C. less than 15.0 (see the new Blue Book, the one with an SDRC bike and an SDRC car on the cover, for the new rule).
So, yes, your C-12 at -0.5 certainly looks like it will qualify.
Jim