Mazda has the highest compression ratio gas engine and lowest compression ratio diesel engine (for an automobile) both at 14:1 CR. It seems like they did a number of supporting changes to help both engines work well with unconventional CRs.
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html
http://www.mazda.com/mazdaspirit/skyactiv/engine/skyactiv-g.html