OKAY30R Subaru Engine Subaru’s OKAY30R was a 3.0-litre horizontally-opposed (or ‘boxer’) six-cylinder petrol engine. Replacing Subaru’s OKAY30D, the OKAY30R engine was first introduced in the Subaru BP Outback 3.0R in 2003 and subsequently offered in the Subaru BL/BP Liberty 3.0R and Subaru Tribeca.Compared to the OKAY30D engine, changes for the OKAY30R included: A lighter cylinder