IXL Oil Additive

I went to a flea market in Yuma Arizona and watched a demo for IXL oil additive .I was impressed with the demonstration and was wondering if it would be feasible to add it to my ML500. In the owners manual it states that no oil additives should be added, as it would void the warranty. The IXL sales person says it will not harm the engine or void the warranty, only improve horsepower, better mileage and extend the live of the engine.
My question to the techs is would it be to the benefit to the engine.