Coop, it probably isn't going to matter much. IF your 5-40 shears at all, it will be similar in operating temp viscosity to the 0-30. The GC 0-30 reportedly is more shear-resistant than most oils. It would probably take a synthetic 5-40 to have a chance to stay in grade for long! Does the RAV-4 recommend a 5-30? If so, sure, GC is appropriate.