I am a member of the Toyota FJ Cruiser forum, they went through the same questions over there. Several guys bought them solely to test and gave the results. They were all returned because of no fuel gain, but they don't have a true 90 day money back guarantee. "Reconditioning was needed". Basically when you install it they tell you easy acceleration, role to stops.... this style of driving would save you gas normally. If you are truely interested buy one and give it a shot, you can always return it.