Did you mention to him what you use?
Did you steer him over to BITOG or ask him if he's one of us??
No I didn't - he had several bottles in a box in his trunk. I could see all the about 1/4 or so tops of all the bottles. Took 1 bottle out, shook it well and poured it in the tank, then did his filling. Seemed proud (cracked a smile) dumping it in the tank. Had a rag in one hand I guess for spill, but he didn't need the rag and put it back in the box.
I was thinking "he's going to give me the empty bottle so I would stop at a auto store to get this magical stuff, or maybe hope I offer some bucks to buy one on the spot".
I should have told him I use two bottles every fill so my car will run twice as long as his. Three bottles if I'm feeling naughty.