I noticed that Clarity PHEV tire size is the same as base (18 inch) Tesla Model 3 (Tesla has higher load rating). This is good, because with Model 3 selling like hot cakes, I assume there will be a wide range of efficient tires available in the future. Maybe then even come up with more efficient tires in a year or two, who knows.
Michelin has a made a special quieter performance tire for Telsa in 20" but I've not seen them available in 18" OEM size. "Limited sizes of the Michelin Pilot Sport 4S are available with Michelin Acoustic Technology, which involves the manufacturer adhering a layer of sound-absorbing foam to the inner liner of the tire to reduce cabin noise in the vehicle."
OEM clarity tires are $228 each with 480 wear rating. Better but not good. I believe any low rolling resistance tire will work, the difference in mileage shouldn't be that significant as long as it is low rolling resistance. Interestingly there is a Ford version of the same tire that is $210. They appear to be identical.