Among the things that could bring about abnormal oil usage is apex seal failure which leads to greater clearance in between the rotor and housing. This enables inside oil leakage into the combustion chamber resulting in grey smoke through the exhaust. Just after having burned by two ‘small-mileage’ 13Bs from https://paxtonbxmbi.shotblogs.com/the-2-minute-rule-for-jdm-mazda-rx-7-fd-13b-rew-engine-for-sale-51951373