The later certified  912 ULS variant has a compression ratio of 11:1, and requires 91-octane ("premium") auto gas (100LL leaded avgas can be used, sparingly).
The later version of the 912 ULS engine, certified for use, has a compression ratio of 11:1. It requires premium gasoline (91 octane) and 100LL leaded avgas can be used in limited quantities.