What is your current "Oil Change Interval" (oci)and what brand, weight are you using? Include your reasons for your current prescription and the vehicle. List the filter too! Here is mine: -2003 Toyota Tacoma 2.7l -gets 5w30 Mobil 1 Synthetic. Its changed every 6 months or 7500 miles. Using Wix filter. I do the changes. -1995 Toyota 4-Runner 3.0l-gets 10w30 Mobil 1 and 150ml of 15w50. Its changed every 6 months regardless of mileage. Using Toyota filters. I do the changes. Reasons for my prescription. Both vehicles are in the severe service catagory so synthetics are used. I will keep these vehicle until they die.