Is it safe to use a synthetic alternative like "Motul MULTI ATF Fully Synthetic" which Opie oils list as suitable for the car, or should I stick to the basic mineral Dexron IID?
you can safely run Dexron III updates. The motul states that its compatible with all older Dexron requirements (except Dexron Vi), so you should be fine to use it.
you can safely run Dexron III updates. The motul states that its compatible with all older Dexron requirements (except Dexron Vi), so you should be fine to use it.