A method is disclosed for preparing an elastomeric base composition comprising: (I) mixing by an extrusion process (A) a fluorocarbon elastomer with (B) an optional compatibilizer, (C) an optional catalyst (D) a silicone base comprising a curable organopolysiloxane, (E), an optional crosslinking agent (F) a cure agent in an amount sufficient to cure said organopolysiloxane; and (II) dynamically vulcanizing the organopolysiloxane, wherein the weight ratio of fluorocarbon elastomer (A) to silicone base (B) in the elastomeric base composition ranges from 95:5 to 30:70. The cured rubber compositions obtained from the elastomeric base compositions herein have good fuel resistance properties.