Puffin'smoke,
Amsoil's recommendation on the Turbo Diesel enigines is:"up to 2 times longer or 6 Months with Oil Analysis. When they say 2 times longer, they mean "equipment Manufacturer's recommendation". I have gone over 140,000 miles on only one oil drain using the by-pass filtration system and doing Oil Analysis every 10,000 miles. The filters were changed only when the oil lab said to change them.
On another note, I have some customers that are not using the by-pass system that are getting 12,000 mile drain intervals, but changing the filter element every 6 months. One such customer has over 350,000 on his truck with no problems!
Personally, I beleive in the
Oil Analysis Program!
Wayne
amsoilman