Hi I have 1994 cummins turbo diesel. And i found a good deal on amsoil. And changed the oil in it. What I am doing is changing just the filter every 6 months. And adding 2 quarts. But adding amsoil is way to expensive. So I heard it is not good to run full synthetic in high mileage cars. I was going to start to add start adding rottela t full synthetic. But it is not good to run full syn in high mileage cars. But amsoil I heard is different than other full syns. What do you guys think. Any help would be great.