I'd say it's closer to 3.5 hours, maybe 4 if there is inclement weather
We drove from Skye (Portree) to Oban (breaking journey in Glencoe, I'd certainly add time there if your itinerary allows) last September. As we had driven to Skye over the bridge from Inverness, we opted for the car ferry route from Armadale to Mallaig while returning to the mainland. That's an option too - if the winter schedule works for you https://www.calmac.co.uk/mallaig-armadale-sk… We enjoyed driving through Morar/Arisaig/Glenfinnan en route. I find viamichelin.com more reliable for drive times than Google Maps.