We did this very route at the beginning of last week over a couple of days and thoroughly enjoyed it. I'd add a couple of things though .....
Head down the, in places, single track road to the coast at Easdale (just South of Oban) and spend the night there. There's a huge car park in the village beside the art gallery which allows overnight parking. The sign says £10 per night but when I asked in the gallery the friendly woman said help yourself, no charge!
Head East from Oban to Loch Awe and visit the Ben Cruachan Underground Power Station, it's a fascinating place.
Visit Cruachan