To obtain a vibrationproof rubber compsn. which is excellent in oil resistance, durability, and adhesion to a polyamide and can be used as a support of an automotive vibrationproof rubber by compounding a high-mol.-wt. ethylene- propylene-nonconjugated diene copolymer as the base rubber with a silane having a double bond, an org. peroxide, and a carbon black having a specified DBP absorption.

The nonconjugated diene copolymer (A) used has a number average mol.wt. of 200,000 or higher and viscosity (ML1+4, 121°C) of 120 or higher. An example of the silane (B) having a double bond is vinyltrimethoxysilane. The org. peroxide (C) is, e.g. dicumyl peroxide. A carbon black (D) having a DBP absorption of 120ml/100g or higher is used. 100 pts.wt. ingredient A is compounded with 2-6 pts.wt. ingredient B, 2-8 pts.wt. ingredient C, and 30 pts.wt. ingredient D.