Most if not all Hyundai engines are extremely tolerant to higher viscosity oil and higher HTHS. I see very little difference in power or fuel economy going from 5w-30 to 15w-50, I also have lower oil temps running a higher viscosity.
Nope, many GDI/TGDI engines have this problem, HK takes it to another level and their engines are more likely to catastrophically fail if you aren't on top of it.
Sufficient viscosity and frequent changes are the key to Hyundai and Kia engine longevity. No oil is going to prevent fuel dilution and hard abrasive carbon soot from wearing you engine, but getting that crud out by changing the oil will.
With all those codes I'd first do a compression test before throwing plugs/coils/injectors/vvt solenoids at it. Also check the oil, low oil will set those kinds of timing codes, if the level is good and compression checks out (at least 158psi) then the solenoids are probably clogged up.
The...
One thing I really agree with him on is you can't just use TBN to determine proper drain intervals with modern ultra low sulfur fuels. Between that and that engine builder from Nissan/Infiniti telling people if they want their engine to last hundreds of thousands of miles they should change...
If I've learned anything being both a mechanic and a rideshare driver it's that most people drive like an idiot with 1 foot on the gas and one on the brake.
I had the same issue until I started using a 50 grade in my Accent. I have seen plenty of modern engines (believe it or not Subaru is the worst) turn their 0w20 into something the consistency of water. Fuel dilution is my guess
I've put thousands of ecogard filters on vehicles and only once did I have a leak and it was an old stock filter that sat on a shelf for years, gasket blew out on startup.