Not too much talk on the forums about this stuff. But..
I used the Lucal Oil Additive with Valvoline synpower 5-30 (I always use Mobil 1 but got Valv. for free) in my last oil change, I should have not even ran it after mixing it in and seeing that the viscosity of it is the same as jelly. Had it in the truck for about 500 miles before I had to change it back out to Mobil1. My drive to work has a few straight uphill freeway miles in it and I noticed it worked harder to get up those straightaways by downshifting more and higher rpms. Also, having laid on the gas from time to time it dogged bad and ran like it was barely on 6cyl. Im no fluid guru in technical terms, but the Lucas is garbage. My oil psi was way too high with it in and I'm suprised I didnt blow a gasket on something. Changed back to Mobil1 and its back to normal. Read up on that stuff if you plan on using it, as I just took word of mouth on how good it is supposed to be and learned otherwise