Here is a cutout of the most recent Prolong thread. Seems to work.
Originally Posted By: BenzFella
Little background: The vehicle is 2007 Toyota Camry, 4 cyl, currently 120k miles. Since new it always had premium synthetics with occasional boutique oils here and there. Never more than 5k miles on a OCI, therefore the metal seen through the fill hole is as shiny as it gets.
About 1k miles after last oil change I got a bottle of "Prolong" metal friction additive for free. Figured that it will not do any damage and used it to top off the oil level. Instantly the engine became a bit smoother. The slightest noises smoothened out. That is when I realized how loud my engine was and how quiet it can be. It has been 3k miles since I added Prolong into the crankcase. Engine is still very smooth, and gained 2mpg across the board, for the first time since new. Overall I am very satisfied with the product. Probably will use it always from now on. Also my normal oil consumption is 1qt every 3000 miles. Since adding "Prolong" the oil level have not moved on the dipstick.