Q. Why does AMSOIL say to change the AMSOIL SDF Oil Filter at six months regardless of the mileage? I have only driven 5000 miles and figure that I could go the whole year without changing it and be good.

A. Once an engine is running with new oil, byproducts of combustion are introduced into the oil. These byproducts are harmful chemicals that continue to degrade the integrity of the motor oil as well as the oil filter media even though the engine may be off. This is why a time limit is published as well as mileage. Short trip driving can be just as detrimental to motor oil and filters as high mileage use, and even more so in some cases. It’s possible that the oil is still intact at the end of the published time limit, but oil analysis would be needed to verify this. Heavy trucks use this practice regularly, however in small sump capacity engines, the cost of the test is nearly as much as the cost of an oil change.