[HawgRyder]

In some trucks they run a second oil circulation system that employs another filter.
This takes out a lot more debris than the full pressure system that oils the bearings, etc.
In this type of engine/installation, the oil lasts much longer with the addition of additives.
The reason for not changing as pften as we do is the size of the system, some hold 55 or 60 quarts/liters.
So the cost factor affects the profit in these working trucks.
Bob