I've done my share of research and 5000 mile intervals are OK with the TCH...the 4 cyl ICE doesn't run all the time and,when it is running,it has the load assist from the MG's...3000 mile interval is still good and fairly cheap insurance for all other ICE's...4 or 5 qts of regular oil won't break the bank.
I've used synthtetic oils and they,in many folk's opinions,are best in high heat,high stress (like racing) situations or in very cold climates...zero and below...my 07 TCH is doing just fine on 5W-25(I blend Valvoline 5W-20 with 5W-30) why? I believe 0W anything is a bit too thin and I won't go 5W-30 because the ICE may be running a tight bearing clearance(less than .0002)...so I compromise and the 4cyl is running just fine...a lot of the 10000 mile change intervals,IMHO,have more to do with perceived long range maintenance benefits to fleet buyers...
gasoline mileage is fine,BTW,I saw 49 mpg just the other day on a non-AC required mild day...no rain and no wind either...
Using any oil besides 0w-20 requires 5000 mile intervals on a 2012 THC. I don't know what your basis for saying 0W is a bit too thin, but Toyota recommends 0W-20 for 2012 THC. Your reasoning for a 5,000 miles for the hybrid ICE over other ICE 3,000 miles oil changes seems a little bogus seeing that a hybrid is on a on off on cycle. As far as I'm concerned, the 3,000 mile oil change under normal driving has long been abandoned by the manufactures. My 2000 Honda Civic recommended oil changes at 7,500 miles. I went with a 10,000 mile interval, went ten years and 161,000 miles before trading it. Engine from day one to day 10 years consumed 1/2 quart oil every 10,000 miles. I don't change my oil as I live in an apartment. Your comment that lot of the 10000 mile change intervals have more to do with perceived long range maintenance benefits to fleet buyers has no basis at all.
My 2010 CR-V uses 0W-20, has 42,000 miles, oil is changed around 8,500 miles, depending when the oil wear indicator gets to 15% or less. Now that I have the 2012 YCH, the CR-V will be on a yearly oil change as I'll be lucky to do 5,000 miles a year on it. My TCH will be on a 10,000 mile oil change interval. I expect the THC to last ten years or more, more and likely exceeding my remaining years of life on plant Earth.