sorry i dont have a route map, but i started the costal road from ras al had and headed down towards masirah. i asked so many people along the way about the tarmac road and got many different answers, in the end i just went and was in for a surprise. after you reach al ashkara continue down the road, its newly paved and you will be fine with gas. but about 30 km from masirah the road ends, at that time march 09, i actually reached the part where the contractor was still paving the road, after that i rode on a gravel terrible road, i think by now they must have finished it and you will not have any problems.
you will then reach Muhut and head down to Duqum, after duqum head down to Rima where you will get to a small roundabout, take a right on that roundabout and head towards Nimir. when i reached nimir i was near out of fuel, this is the tricky part, there is a gas station in the area but its not a typical gas station that you come across, its actually a pump for the oil field contractors in the area, if it wasnt for some truckers who lead me there i would have missed it. ask around and you will be fine.
after that its a newly paved road all the way to thumrayt then down to salalah.