My !personal! experience with N52B30 puts a red warning light ref mileage, especially if the car was driven to/at its limits (as I am used to drive mine almost all time). But, to the contrary, someone linked a N52B30 withstanding over 400.000 miles in good condition. Some guidance may be taken from overall average fuel consumption (if reliably available): My N5230 died from wear at 160.000 miles covered with overall average close to 15mpg, that linked N52B30 withstood 400.000miles while averaging 27mpg only!