[Beaker]

No HCCI has nothing to do with flex fuel. It just tries to merge diesel compression ratios and injection technology with a gasoline engine as he said. A true HCCI engine doesn't use spark plugs like diesel engines as well. Currently they have them working up to about 3-4,000 rpm. There are hybrid designs that integrate the use of a spark plug for higher rpm operation but I'm not sure what they do with the compression to resist detonation. The idea is to try and take advantage of diesel like efficiencies with regular gas.

Now honestly a fuel like E-85 would probably be a better fuel for an engine like this due to its higher octane rating.