Provided are elastomeric compositions, such as a tire innerliner, comprising at least one isobutylene based elastomer and at least one hydrocarbon fluid additive ("HFA"). The compositions have improved cold temperature properties and are particularly useful as tire innerliners for an aircraft tire. The use of a HFA in the elastomeric composition may allow for the use of reduced amounts of secondary elastomers, such as natural rubber, while allowing for an improved balance in the composition's brittleness and permeability properties. Examples of useful HFAs include polyalphaolefins, high purity hydrocarbon fluids, and water white group III mineral oils.