My daughter follows the add a gt a month OIC in a 1990 tercel that holds 3 gts. I change it when she gets home but she puts 7-8k on the above method. The above method is an improvement over her previous method which was not even to add. Last summer I added 2 gts to get her on the dipstick. Besides sending her Pepboy bucks for an OIC, any suggestions. I'm thinking 15-40 delo since she's in San Diego and changing the oil filter at least at 3K to improve her continuous change as tercel filter is right there in front center.