Not wishing to pee on your bonfire, but if someone claims 10%, in reality this might actually equate to 5% in the real world & there will be a trade off somewhere. E.g. I originally had BRP Viper props on my Etecs, I switched to Mercury Rev4 which used around 10% more fuel than the Vipers, but the improved handling, holeshot & grip was worth the 10% fuel cost. I could claim that the Vipers would save me 10% over my current props, but would I want to pay the price? Nope!
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5