My wife and I will be in Scotland for the first 2 weeks in June. The first week will be in Edinburgh and will include 2 or 3 day trips still to be determined. The 2nd week we will rent a car and go from Edinburgh-Inverness-Isle of Mull-Glasgow. Stops along the way still to be determined but the hope is to make Inverness and Mull a home base for a night or two each. From what I've read so far is that driving will be slow through the Highlands, so a general question-not accounting for frequent stops for scenery and sites, how much should I trust Google Maps for driving times? Is their a general time I should add to Google's driving time from Edinburgh to Inverness and Inverness to Oban? My main focus right now is making sure we don't get caught in the middle of nowhere after dark and so giving myself some leeway to get to final destinations each day.
I usually add a third to Google times.
You're right to plan so as to avoid having to drive on secondary roads after dark. However, since you'll be there in June, you'll have lo-o-ong hours of daylight. We've been to Scotland in May and already noticed that by 9 PM it is still light. The challenge is to remember to find a restaurant to have dinner before it gets to be so late in the evening that only pubs are open!