Buckhunter, We have numerous plants across the US and Canada, and the type of filters run the whole length of filter manufacturers. I am task with trying to get the plants into standardizing this, among other things, but I will give you the information that we as a reliability group have researched. The first thing is that typically the bypass valve is located in the filter head and not the filter itself. Second from all of the research we have done comparing different brands, cost application and such we have recommended to all of our manufacturing facilities to convert to Donaldson filters. Donaldson makes a wide range of high quality filters for numerous applications. We have also found that they are very cost attractive. Information is easily obtained with respect to Beta ratings, media, and testing results. This can not be said for some of the other filter manufacturers. I am not saying that other filter manufacturers do not make good filters, it is just sometimes it is hard to get the information needed to make sound decisions. I am really vendor neutral and don't care what brand is used as long as it meets the specifications required by our group, but you wanted to know what we use. This is just a suggestion. Check out Donaldson filters on line. But enough jay-walking on that, in regard to bypass filtration, all rolling stock equipment typically has a bypass in the filter head, this helps to prevent lubrication starvation at start-up. The oil is cold and has a lot higher viscosity that at the normal operating temp. When in bypass the oil can reach the upper end of the engine and as the temp comes up the pressure drop across the filter decreases, closing the bypass. I hope this has helped in some way. Please don't be duped by salesmen that tout the presence of a bypass valve incorperated into their filter as an added value, it really isin't