I inherited a never-run MS170 and an unopened gallon of Motomix last year. The unadjustable-carb saw ran really rich on the Motomix, contrary to what I’ve read here about most of them running borderline too lean. It blubbered like a MX bike trying to race with the choke left on: pretty much unusable. But it didn’t smell bad; I thought it smelled kind of like race gas exhaust.
The saw ran, and continues to run, much better on my normal 32:1 premix I use in my other ***.
My new Redmax strato trimmer loved the Motomix though, and also smelled like race gas exhaust and emitted no visible smoke. The trimmer also runs well on the 32:1, but smokes a little on cold startup.
Recently I tried Stihl HP Ultra at 32:1 and it doesn’t smell exactly like the Motomix did, but vaguely similar. I think the Motomix smell comes from a combination of the fuel and the oil in it.
EDIT: for some reason I got censored for trying to abbreviate Outdoor Power Equipment...?