Fuel System Cleaner killing fuel economy?

[TheEdgeofSanity]

So, I put a bottle of Chevron Techron Synthetic Fuel System Cleaner in a full tank of gas and I noticed I am getting shit for mileage on this tank of gas. I usually get 100-150 miles from full to the 3/4 mark but this time I have a little over 80 miles and I am nearing a half tank.

Is it normal for the stuff to cut down the efficiency of the fuel? I've never noticed this before while using fuel system cleaner, yet this techron stuff was recommended by a GM certified mechanic. maybe because its more condensed, it dilutes the gas more?

I'm just worried because with the way it's going, I think I am only getting less than 20 to the gallon and thats HORRIBLE considering I am broke and barely can afford gas while getting 25-30 per gallon!