Hyundai/KIa have some problematic engines, being both design and probably a bit by the way they "tune them" IE ECU fuel mapping/ignition/cam phasing. Probably 1st or 2nd of the worst of the top 20 automotive manufacture brands that carry some form of this issue. While there are hundreds of thousands of outliers that run with no issues. There are a huge chunk of them that will be problematic, because of the above issues, that are over the top compared to other manufactures in occurrences and degree.
Example my car, 2018 Hyundai Kona AWD 1.6T one of their better designed and less problematic engines by the way. The car went from a stage 1 tune to a stage 2 tune around 10,000 to 15,000 miles. It has 72,000 now. I was playing around with different oils Mobil 1 vanilla, Mobil1 Extended, AMSOIL Signature Series, Pennzoil Ultra/Platinum/Euro L, Mobil 1 Euro, Castrol Euro, Quaker State Euro, Mobil 1 ESP 5w-30 (old formula), Motul 8100-Clean 5w-40 Gen 1 & Gen 2, Redline Performance 5w-30 Euro. (Motul V300 as another cleaner AFTER the Redline incident below.) I change oil @ or before 3,000 miles with all of these oils through the life of my car. Tuned Hyundai/Kia engines are VERY hard on oil, my oil is blackish at 3,000 miles. Yes. I know black does not mean bad, but keeping this engine together and clean with 23 psi and it getting fully thrashed on......cost of doing business. I am past "rough service". My car was using Mobil 1 ESP 5w-30 for the last 1.5 years just before trying Redline Performance Euro.
I live in Minnesota (unfortunately). I am a short tripper and I warm my car up for 3-5 mins every time I start it, even in summer depending on temperature to expand my very short pistons a bit, too many Hy/Kia's with worn skirts. I had very bad fuel dilution very early on and tracked it for wear because I knew what I was getting into before buying it new. I had 10 Polaris Labs oil samples kit before I took ownership because I knew I had a diluter from day 1, and it was. At it's height I was adding 1.5qt of fuel/moisture during winter. I would check my oil at 1,500 miles and suck out oil of the dipstick as it was .75 qts high and dump at 3,000 with the same gain again. High pressure fuel pump leaks were never an issue as I monitored it, with holding pressure after turn of. Then one day I tried Redline Performance 5w-30, I went to suck out my usual .75 gain and it was dead nuts on the full mark, couldn't believe what I saw. My fuel dilution was gone. The higher Ester in this oil had to of broke up the ring jam. I think it had to be the oil ring too, that would allow flooding of fuel past the rings and into the oil. I did not have overly high wear# so I just eventually did not worry about fuel dilution. Some people here where all worried and rightfully so I guess, on theirs. I saw no over the top wear so I thought it was what it was, till it went away.
So now I use Valvoline Restore & Protect during late fall, winter, and early spring to keep my ring pack clean and during summer I was using Motul 8100-Clean 5w-40 Gen 2 with 1 Qt 40wt HPL engine cleaner every other change to keep the rings clean. I have since went this summer to Valvoline Euro 5w-40 to keep closer the same manufacture add packs IF they are I have no idea but better then just guessing with another brand. As I stupidly cocktail my fall/winter/spring Valvoline Restore and Protect with 1qt Valvoline Euro 5w-40 to increase HTHS #s since my car is a turbo car. I refuse to ever have jammed rings again and Valvoline Restore and Protect is the right oil for the job especially on Hyundai/Kia engines where even the top tier Walmart shelf oil and boutiques have issues with keeping ring packs un jammed. And yes, I have pulled away with time, that I need any form of boutique oil to keep this motor healthy, I am only doing shelf oil now a days. Especially with certain oils that fully clean ring packs better/same then the best Ester/AN boutiques. And my car I think??? can be an example that top tier oils do not mean you have a truly CLEAN ring pack, unless you pick one that can do the ring cleaning job it was designed for.
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