I have been using Kixx oils for my cars for the last 01 year and found it very good at a reasonable price, KIXX 5w30 SN/CF and KIXX 5W40 PAO SN/CF ACEA C3 are very advance as compare to their counterpart available in the market. It ensures excellent cleanliness with fuel efficiency and extended mileage (oil replacement interval).
Lot of people here recommend Caltex Havoline (Chevron) brand over KIXX and condemning KIXX with loud words but I hope while recommending other brands over KIXX they must be aware and known to fact that Kixx is also a brand of CHEVRON & LG {Kixx is Engine Oil Brand of GS Caltex which was founded in 1967 as a 50/50 joint venture between Chevron and LG Group of South Koera}.
Further KIXX is official oil of several Korean OEM like Kia, Hyundai, Doosan etc, whereas ZIC is not, but people here are recommending ZIC over KIXX, i am not condemning ZIC, it is also a good oil but if you can get original one. So far in our market Havoline & ZIC both have been copied a lot, if you can get directly from its main dealer then its good otherwise.
Some are comparing KIXX with Liqui Moly which is unfair, I also used liqui moly for several years but I found it over rated and over priced, after shifting to KIXX i didnt find any degradation in performance, engine cleanliness, or fuel efficiency but found same performance (may be improved) having less burden on my pocket.
Kixx 5W40 SN/CF is too good and recommended oil to be used for DOHC, VTI and other advanced engines.
Engine Oils starting with 5W is too thin and not recommended for very old engines (1980 - 1990) who's OEM recommendation starts with 10W or 20W(at least) to start with.