In an ideal world, the rotary engine metered oil pump should inject an ashless oil designed to burn in the combustion chamber and use a four-cycle oil in the crankcase for the eccentric shaft, rotor bearings and thrust bearings. For the street, Mazda simplified the OE system to use just one oil, that being a typical four-cycle oil for both the e-shaft as well as the combustion chamber. Royal Purple recommends using our standard 2-Cycle TCW III if the metered oil pump is still enabled. The two-cycle oil being added to the fuel tank is in addition to what Mazda designed to inject and acts as a supplement or insurance. Depending upon which engine, the level of modifications (street port, Bridgeport, peripheral port, nitrous turbocharged) and application, the typical mix ratio could vary from 200:1 to 800:1.

For a pure racing application where the metered oil pump has been disabled or removed, again based on the actual engine and modification level, the ratio could vary from 150:1 to 600:1. For this application, we recommend our 2-Cycle TCW III Racing or the standard 2-Cycle TCW III.

A stock FD twin turbo 13B with the MOP oil injection system can typically use about one quart per 1500 miles under hard street driving. If this vehicle is getting 15 mpg, the gasoline to oil ratio is 400:1. If the oil consumption on this vehicle reduces to 1 quart per 2500 miles and fuel efficiency increases to 20 mpg, the gasoline to oil ratio increases to 600:1. The stock metering oil pump is a great system as it varies with throttle position (load on the engine). Pre-mixing has to be calculated for the ‘worst case’ that will be seen by the engine for that fuel load. Under racing conditions, that’s wide open throttle at racing rpms. This means that at idle, the ratio may be slightly fat (rich).

The stock metering oil pump is a great system as it varies with throttle position (load on the engine).