fuel or oil

Was thinking a about trying one of these aditive things you can buy where you pour one in the fuel tank and another in the oil to make the engine quieter and more efficient. Anyone used one and any recomendations. Petrol engine BTW! Thanks

Hi Does anyone use any type of fuel or oil additive to increase mpg or reduce wear? I have used the Wynns oil and fuel treatment on previous cars but wanted to know if anybody has any first hand storys on this or other products in Mercs? Cheers Mark