In china Beijing all K5 is NU engine .Their petrol is RON 90 AND RON 92 only.Who say cannot use this petrol.
The different is is lower RON is cannot withstand higher compression in piston.Fuel ratio vs compression in piston is lower and the burning speed is faster.Thats why the computer is auto adjust to lower air mix ratio in piston.
Higher RON only get efficient in high performance engine cause it require high compression in piston to get efficient power .
During fuel inject to piston with high pressure and compress to max,it can burn without delay,no waste .In germany have petrol station sell RON 99 to cater Porsche and super charge engine,cause using petrol lower than that the engine is feel surge. Some more got unburnt fuel in exzos.

This post has been edited by izamd: Oct 28 2012, 12:03 PM

Some one can find info about K5 NU engine and CVVT in kia web site China.It written in mandrin ,may somebody can translate to layman english here.I currently in beijing in saw a lot K5 there.Their petrol expensive ,,convert RM 4.50 1 liter RON 95.

Even lamboghini also got problem. Check in youtube and Google news one owner in china smash the new lambo cause cannot stand the defects.