I am now on the maintenance dose on my 99 Crown Vic. I put in Valvoline synthetic along with 3 oz ARX.I usually drive 5K with synthetic oil and then change the filter and add 1 quart then drive another 5K and change the oil. When I reach 5K on this oil and I change the filter would it be neccessary to add another 3oz of ARX or should I wait until 10K when I change the oil?
