I've only seen one test and it was flawed. But even that test said Power Service increased the lubricity of the fuel. The problem with the test is they used untreated fuel (as a worse case). Since you can't buy that at the pump it was of limited value. Secondly they didn't follow industry standards for testing. All they did is test each additive once, statistically speaking that's not how a test should be done. I think that PS is not the best option on the market but it's easy and cheap to get.
I think Opti-lube would be a better option for most but the XPD only goes down to -20. That means I would need to use their winter blend which came in a little better in that test than PS but no where near as good as the XPD.