First, why is premixing, or for that matter oil injection required on a rotary engine? Ever since the earliest days of rotary engines, controlling wear of the apex seals has been a challenge. Apex seals have a unique place in the world of internal combustion engines. Rotaries operate like a two stroke engine. Every time a face approaches the spark plugs, combustion occurs. Contrast this with a conventional 4-cycle engine where the exhaust/intake stroke is cooler and lowers the heat load on the parts. Heat builds and remains in the parts easier in a rotary engine. To add to this challenge, the apex seal travels the longest distance of all the engine parts. This whipping and wiping action causes wear issues and a propensity to chatter. Metallurgy and design helps to minimize the issue, but in the end lubrication of the surface is required. Having a thin boundary layer of oil assists the seals in remaining viable for many years. From day one, Mazda has employed oil metering to automate the oil injection process. A small amount of oil is drawn from the oil sump and metered into the fuel and air stream to provide the sacrificial lubrication required. As years have progressed, Mazda has faced a continuing challenge of providing the needed lubrication while still meeting the United States and world emission regulations. By altering the injection location, injector numbers, etc. they have kept barely ahead of the standards. There are some years of rotary cars that the injection profile was so stingy, that it easily becomes a wear issue for the engine. Unless the car is operated in a best practices method, the engine will wear itself out prematurely. In addition to this, there are operating scenarios that require more than what oil injection alone can provide. Welcome to the world of premixing.