so, as a rotary owner i can dabble on that bit. you pre mix if you delete you OMP or oil metering pump. this was a rod that connected to your throttle body and would pump oil into the TB from the pan!! this would make rotaries require more frequent oil changes. Mazda did this bc they couldnt sell the car as "hey small side note, you need to pour oil in your tank whenever you fill up. gucci? cool"
yeah naw, people wouldnt wanna do that or forget/neglect and BOOM goes rotary.
us gear heads however dont want gross oil pan oil being used to lubricate the apex seals in the engine so we delete the OMP/rod/lines and switch to premixing.
Also when the OMP would fail there would be no signs, your engine would just seize lol
rotaries are CAR PEOPLE cars. they're really cool and very simple once you understand them. with the OMP still hooked up you can pre mix 1/2 oz per gal in your tank. if you delete it, you should run 1oz per gal in your tank. idr what the ratio's are