I used Motor Honey a lot in the first car I bought, a 1983 Monte Carlo, with a tired 3.8L V6 engine. The thing smoked like a freight train and drank oil from the day I bought it, and I figured WTH, Motor Honey can't hurt. I probably went through 100 qt's of the stuff in the 80k miles that I drove the Monte. This was from 1989-1993.
Did Motor Honey help? "Yes", because it slowed the oil consumption.
Did Motor Honey cause any damage? In the climate here in North AL, I doubt the thickness of MH caused any damage, but I have no way of knowing.
Also keep in mind that during the time I used MH, all I knew about oil was that my mechanic Father (G0d rest his soul) used 10w40 in everything (so I did, too), and he told me that Pennzoil would sludge up an engine, so I didn't use that. IIRC, I used a lot of Castrol & QS in the Monte during that time.