Mercury - Oil Tank Assembly Two-Stroke OptiMax Lubrication 833069T6. Overview. This oil tank assembly is a solid fix for an older OptiMax that's starting to show its age. When the original tank gets brittle or the grommets crack, the engine can act a little unpredictable, so swapping the tank is an easy way to bring things back to normal. The parts in this kit line up the way they should, and the hardware makes the job pretty straightforward. It's one of those replacements that gives you some pe