Yes, the executor has the legal authority to let you (or anyone) use one of the assets of the estate if it is in the interest of the estate and/or the beneficiaries. Since you are a beneficiary and the other beneficiaries do not object, he can let you do this. He probably should have you sign an agreement to pay some of the car costs--maybe all your gas and part of the insurance--so that way, the other beneficiares do not incur any costs due to your use, and you do not get some inappropriate gain over them, but that's only a suggestion: as long as the other beneficiaries are on-board with this (though he should get their consent in writing, to protect himself), he can let you use the car without any payments.