With a hybrid constantly starting/stopping the engine and perhaps seeing even lower oil temperatures than a regular vehicle in cold weather I think synthetic oil is worth it in in colder climates. In warm weather it'd make very little difference.
I'll keep using Pennzoil Platinum 5w-30 in my Prius just because. I feel comfortable running a quality synthetic 7500-8000 miles in this car, and that makes it a decent value from a priceerformance standpoint.
I was curious how exactly this works too.... since, most of the "benefit" of these hybrids is inter-city, stop and go traffic....where the engine is for the most part "off" and merely running on the battery (and obviously, cycling back and forth to keep it charged).....
Wouldn't this "engine on" (to charge.....), ooooopppps, here's a stop sign, brakes applied, better shut the "engine off" to conserve power" about equivalent to "short tripping" since the engine is being "rarely" or "barely" ran enough to actually "warm up" the oil......?
Then I was thinking, perhaps that's why they spec a 0W-20 (I know Toyota for sure....) - being a lighter weight oil, perhaps it's easier to burn off possible fuel/moisture in the light, 0W-20 motor oil...?
I work at a Toyota dealer & we put synthetic 5w-30 in all the Prius we service here. Looking at the SDS it lists 0w-20 upto 10w-30 as suitable options.