That should make you happy, it means your fuel system is probably in good condition and all is well. I've had the same results, I even went as far as using two bottles and rigging up a mini fuel tank and gone for a spin around the neighborhood to really purge things, but I've found if everything is in good condition then that is the result.

On the other hand, my old 300SD had some of that Seattle hippie sauce in it (home brew bio, who knows how well it was brewed/filtered?) and the car HEAVED one giant puff of soot onto the ground during a purge that actually stained the driveway for a few months. It was sluggish and having trouble cold starting before the purge, I mean REALLY sluggish, but once I purged it the thing ran great and all cold start issues were resolved. I swear it must have restored about 30hp. It also stayed that way for the 5 years I owned it.

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1995 E300 Diesel
~300k