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A data point of my own:
About six months ago, having seen the lubricity study and LS1 Tech info, I added TC-W3 to my wife's car at the 1oz./5gal. ratio solely for its purported lubricity benefit.
As a test subject, she and her car are near ideal as far as I can determine. She puts on 400+ miles commuting each week, consistently managing 28.0 mpg. When I would drive her car on the weekend for a trip, I got 30.0 mpg. There's a max variance of about 0.5 to these figures, but the week to week variation was very small.
Immediately and unexpectedly her mileage jumped to 30.0 and weekend driving by me netted a similar increase to 32.0. I was thrilled and also puzzled as to why everyone wasn't doing this too!
I tried it in my pickup and saw the same 6-7 percent increase.
I talked a neighbor into trying it too, and despite high hopes on his part, he saw no increase.
I also puzzled over how this could be helping mileage. The best I could come up with initially was that perhaps cylinder wall to ring pack friction was being reduced, but for it to be enough to provide the increase I was seeing seemed to be stretching it.
I think I found the answer though when I towed a heavy load with my pickup. When merging onto the highway with that heavy load on an moderate uphill grade, the engine experienced some severe preignition ping/knock that I had never heard before. Retarding the timing by 2 degrees in the high load areas fixed that problem.
I believe that the mileage increase is because of the octane reduction caused by adding oil to gasoline. An engine with safe/conservative ignition timing then benefits from the timing "advance" caused by the added oil. I expect that I could see the same mileage increase by more optimally dialing in the timing.
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