For someone who used synthetic oil prior to a Auto-Rx treatment, what do people (with high mileage cars) go back to?
1) back to synthetic oil
2) switch to conventional oil
3) back to synthetic oil with maint. dose of Auto Rx
4) switch to conventional oil with a main. does of Auto Rx
1) back to synthetic oil
2) switch to conventional oil
3) back to synthetic oil with maint. dose of Auto Rx
4) switch to conventional oil with a main. does of Auto Rx