The rotary's reliability under the severest conditions was well proven in Mazda's competition activities in the late 80's and early 90's, including an outright win in the Le Mans 24-hour race for sports racing cars in 1991. A road car is subjected to a different kind of stress, said a Mazda designer responsible for the engine's innards, especially when the 13B-REW's output is increased to 209 kW (280 bhp). Possible problem areas are higher combustion temperature and pressure. The former could be dealt with by the cooling system's heat dissipating capacity. The later was thought to exert extraordinary pressure on the engine's gas sealing.

Apex seal lubrication has become a critical issue. In a race engine, oil supply to the rotor housing by means of injection was precisely monitored and controlled, whereas in the production unit, a larger amount is supplied, just to be on the safe side. Some of the lubricant is fed into the trochoid chamber through a metering nozzle. The previous nozzle's oil passage was 2.0 mm (0.08 in.) in diameter. Negative pressure created in the rotor chamber would cause all the oil within the nozzle to be sucked out. When the engine accelerated rapidly, oil supply could not keep up with the speed. To prevent oil starvation, the previous system supplied a larger amount of oil to be on the safe side. In the new metering nozzle, the passage diameter has been reduced to 0.08 mm (0.003 in.), halving its volume of 0.0005 L (0.03 cu. in.). A new rubber seal is also inserted to fill a gap within the nozzle body where oil used to be sidetracked. Now, there is still some oil left within the nozzle after each suction, so that the lubrication system responds to the apex seal's requirement.